Consider his perspective for a little while.
Most player misbehavior comes from playing around.
A lot of your complaints come from the fact that your player is not taking the game seriously. He is not taking the game seriously. The game is a thing of humor for him. I repeated that for a reason: He's enjoying himself. That's what we tend to do when we play.
Now, with that in mind, let's address the misbehavior:
Clowning
Clowning around is one of the main things that I've encountered as far as issues go. Fortunately, it's not malicious, nor is it particularly damaging. I had a huge problem with this in my first campaign, where I was being all dark, grim, and serious as a novice cyberpunk GM and my players were exploring the effects of their actions on the poor, hapless denizens of the world they were turning into a mess.
This is when they do stuff like buy nine thousand llamas to crash the economy. They're doing it because they can, but they're not ruining your game. My foremost advice when this occurs is to just let it happen. Your player is enjoying himself, and the other players will likely remember it fondly. If you must clamp down on it, be sure to do so with the consensus of other players, instead of just trying to end the "misbehavior" that everyone but you is enjoying.
Redirecting
I've often had players just not be satisfied with the way my campaigns go (and I've been on the participating side of this as well) and decide to intentionally mess with my plot points to redirect the campaign. Ninety percent of the time this has occurred in my games it's been either the result of good in-character roleplaying (for instance, demanding the best gear if the character being played is a greedy, self-serving jerk), or the result of a total lack of interest in the current direction of the campaign.
To deal with redirection, sometimes a soft approach is better. Give your players what they want. Remember that roleplaying is collaborative storytelling, and even though you're doing the lion's share of the writing and creative process you're still responsible for listening to others' inputs when appropriate. Never assume malice when curiosity is just as likely the driving force; I've had players try to kill important NPC's just to see how I'd react, and while it's annoying it's also a way to prove yourself as a good GM by reacting prudently and without exploding (though specifics depend on you and your style).
Trolling
Sometimes players troll you. They'll lock all the other players' characters in a bomb shelter, but reinterpret the meanings of the phrase to result in a deliberate invocation of the "chunky salsa" rule and make everyone re-roll their characters following some explosive goodness. This is usually the result of a player who's bored, discontent, or offended in some way and wants to make the campaign more "fun", perhaps at the expense of everyone else.
The important things to look at when dealing with a troll are rehabilitation or removal. Sometimes it's enough just to ask them to stop, politely. Don't place a "red line", either. It's a great way to get a player to quit in a blaze of glory having killed everyone else's characters. Other times you need to just ask a player to leave temporarily or permanently because their behavior is just so disruptive, but this should be a last resort following other remediation (i.e. the one-on-one chat). Manage trolls privately, not in front of the rest of the group.
A closing note:
One thing you may need to do is set guidelines for your player. If they're constantly playing the same character's mindset, but just remaking them according to different rules, you may need to set boundaries and restrictions on them. Consider very carefully that your player sees things differently than you do; if he doesn't know where things are going, he may very well be disruptive without knowing it.
Also remember that he may be playing the villain in lieu of your NPCs; I've seen this happen multiple times in my group because one player or another doesn't think that the core conflict is interesting, and injects another one to the group dynamic just to liven things up.
If you don't read anything else, read this: Get in your player's head and talk to him before taking any action, communicate your concerns and expectations, and be prepared to use in-game consequences or removal from the group only as a last resort.
To make your question short, and to see if I understood it correctly, we're talking about a player who made his character a certain one and roleplays it entirely different. You added that you think that it comes from inexperience, and that he created this character after you said "no" to some "freak-character"-ideas. You want to help him roleplay the character he created.
As I see it, this problem is made from two smaller ones. The first is that he doesn't see his character as interesting because the character "is normal and normal is boring". The second is that you wanna help him understand why the way he plays the character does not fit the story-world of your game.
Helping him understand that "normal is not boring
This is the more important problem, as it stands in the basis of the entire problem. If he'll see that normal characters can be interesting his "anti-persona" will perish and he'll roleplay a normal character and not a freak one. The main trick here is to show him that normal characters are not entirely normal, i.e. "no person is like the others". In order for that to work, we need to give the character depth.
The easiest way to give depth to a character is through internal conflicts. Having goals and all is nice, but without something that blocks oneself from achieving them it is far less interesting. First thing to do is to go over his character's background and see if he implemented there an internal conflict for his character. If so, show it to him and talk with him about it. If no, sit with him and help him to come with one. The internal conflict doesn't have to be extravagant, but it needs to be there. An example one might be that he loves Vincent's sister but secretly hates Vincent himself, or another like Loves the sister but thinks that he's not good enough for there. I'll take the second one as an example for this section.
The conflict gives us a few things, a few added benefits. It gives the character 2 conflicting goals: "Get the sister and prove that I'm worthy". Now, with those two we also get a kind of an achieving-plan: "If I'll show her that I'm worthy, by getting something amazing done, she'll want me and I'll be able to get her". More than that, the character gets the knowledge that each advancement in order to achieve one goal will drive the other one to the far end.
But the first conflict is even more interesting. The character here has the knowledge that he needs the brother in order to save his lover, but he just can't stand being near the brother. He'll drive the mission onward for two reasons but he'll have doubts about his lover- if he'll marry her he'll be stuck with this brother of hers.
To make long story short, simple conflicts can show the player that even normal characters are interesting and unique. When combined with goals they force the character to take certain steps along the roads, to commit certain actions along the way, that he won't want to do but will make him doubt himself and question himself and see that his problem are far more interesting than those of every freak that he'll encounter.
Another nice way to help him see the importance of conflict is through showing him and analyzing with him certain protagonists that are normal people, from the stories and movies and series (of any form)that he likes. He'll see quite quickly that the conflicts make them interesting.
But he may say that it is not enough. For that there are a few more literary tools that might help him see why normal people are interesting. The first one is having flaws (internal or external) and the second one is using "The Ghost".
Flawed characters are characters that just like normal people aren't perfect. Those flaws can be internal (self-doubts, for example, or a mild paranoia) or they can be external (they're look frightens ordinary people, for once, or a missing hand for the other). The idea is that the character has to deal with the flaw, and one day to find the strength to overcome it. The fight for the overcoming act makes the character far more interesting. A nice example of that can be seen in The Rain Man, where he learns at the end that he can count on strangers/"dumb" persons like he's brother. Another nice example can be seen in the story of The Ugly Duckling who although looking terrible learned to acknowledge himself and to accept the way he looks, to accept his difference.
"The Ghost" is an event from the past that just like a ghost haunts the character to this day. Again, trying to cope with it is what builds a deep character. One example for this can be seen in the movie Inception, where we literally have a ghost- Cob's wife. Another example for this can be seen in the movie Casablanca, where he has to deal with his broken relationship with Ilsa. This Ghost is far more interesting as the originator of the Ghost actually comes back to his life. In Frozen we see another kind of a Ghost- the act that one feels guilty about. Elsa actually killed her sister.
All of these techniques are there for one reason- to make regular people interesting, to give depth to the characters, to make them human beings with goals and drives and psychology.
Helping him see that his character doesn't fit the world
After he understands that he doesn't have to be a freak in order to be interesting, he will be far more understandable about playing a character that fits the world. Then, try to explain to him as calmly as you can what it is in the way he played his character that doesn’t fit the world.
Explain to him that the characters are in a world where being a freak is bad, where achieving one's goals is the ideal. Each and every one for himself, as the saying goes. Give him examples from the way he played his character and analyze with him, in a one-on-one conversation where his way of acting came from. Use the background he created to illustrate to him where your problem comes from.
Then ask him what problems he has with his character, and together try to find a solution. Maybe let him be just a little bit freakish. Maybe he needs to just create a different character. This is basically between you and him. After that show the updated character to the group and get their approval.
When combining those two, you'll get a player who his far more willing to both play the character while also seeing the problems with the way he played his character before.
Combining the two solutions
When combining the two solutions you get a better player, who understands for the future also how to create regular characters that are not freaks yet far more interesting than those freaks will ever be able to be. Furthermore, you get a player who is willing to play his character as written while still making the character fit into the world. Hope any of these helped you.
Best Answer
There seem to be two different things this player is doing that are causing a problem for you, and I'm going to address them separately. I'll start with the simpler of the two.
Your player wants to contradict the rules.
In these situations your player wants something he liked in other games, or because he feels it "makes sense" in the real world. For this, you're going to have to come down on the side of the rules here. The innate abilities of races, the separation of elemental damage types, and the design of combat powers are all a part of the game's balance. To give him these things would be unfair to the other players, who are working within the limits set up by the system.
Now, your player isn't going to like this, because he wants to do more "cool" stuff and his view is clearly that the system is holding him back in this respect. This brings us to the second part.
Your player wants to expand the rules.
Now, where above there was some real risk of your player unbalancing himself with respect to the other players and diminishing their fun, here the player is asking for things that can make the game fun for everyone. He's chafing at the idea that combat powers can't possibily be used out of combat. Why? Because it doesn't make sense.
You should allow the player to use his combat powers out of combat. There is a nice article preserved by the Internet Archive on this. The relevant tweaks are:
The gist of it is that powers do something, and they should certainly also do that something outside of combat. If he wants to try and burn an object with a combat fire power, then treat it as an attack on the object. Just because there's a non-power way of doing something doesn't mean that you have to stop the players from having fun with it.
Your player wants to have fun.
Your ultimate goal at the table isn't to enforce the rules as laid out by Wizards of the Coast. Your ultimate goal is to have a good time with your friends. If you deviate from the rules in little ways that don't harm the balance of the game in order to make it more fun, then so much the better to you.
If you adopt the bonus rule quoted above, share it with your players. You might find they'll do more interesting things out of combat with this reward. And they'll know that using an at-will won't have any mechanical benefit, but it could still seem awesome.
I find it's always best to err on the side of awesome.