The fluff is there to help you as the DM build a coherent fictional world.
First, without any explanation even to the GM, "there's a bearded devil with an intelligent glaive in a cell" seems to not make a lot of sense. "But why didn't they disarm him?" "These guys are devils, why is a devil in a cell?" etc. PCs tend to investigate things and want to know "why," so many times when they do I go to the fluff and let them uncover some of it, it builds the sense in them that the world is a logical one and it's not, as in 1e sometimes, "a huge dragon in a room with only 5' corridors going out of it." Frankly, even if they don't ask, by comforting you the GM that there is a reason (instead of just having a list of rooms with a monster listed in each) it makes you more confident in the game's fiction as well.
Second, they try to do this when there is a chance the PCs will interact with a NPC. In this case, they are in a cell, and can be spoken with without opening the cell door (in fact I am not sure why someone would open the door...). In cases like that, it's nice to have something to hang your hat on. (Not to harp on this specific encounter because you're asking in general, but it just says he's "mad" and "full of rage," it does NOT say he attacks the PCs on sight, which means he could potentially be enlisted as an ally against the villain - a crazy, evil ally, but hey). And don't forget they then get his intelligent glaive, which was a witness to those events. "Hey glaive what was the deal with that guy? "Uhhh...." Or maybe they capture someone else, a guard or whatnot, or they free someone else, and ask them "what was the deal with that devil down there..." There are many, many mouths information like this can issue from.
Third, even a detailed AP is meant to only be the starting off point for your own game. You are expected to expand on it, change it up, mash it up with other stuff, alter it to incorporate your own plots and characters, etc. By adding a little more info to the characters (in the case of the Howling Fiend, the fluff is exactly two sentences long) it provides a plethora of additional expansion hooks that a GM can use during adventure planning. When another devil shows up later, maybe he's not just a random encounter, maybe he's looking for his buddy Szasmir who went MIA a long time ago and now the PCs have a glaive that reeks of him.
Anyway, the actual killing of monsters and NPCs forms a reasonably small part of the overall action in a game of Pathfinder, the investigation and roleplay and all that form a huge part as well, and the fluff is there to fuel it.
This is a pretty interesting question. Without more clarity as @mxyzplk points out, I'll keep this at general suggestions, but I'll be happy to add more clear suggestions later if necessary.
First off, let's look at your ability scores. Your Cha 20 is going to be netting you +2 additional 1st level spells per day, which gives you a total of 5 (I'm going to leave 0th out of the answer, since they're however many times you want). Problem with Oracles is they get 2 1st level spells known per day at 1st level which if I'm not mistaken can't be modified by anything. This is also going to make the saving throw target number for your 1st level spells 16 (10 + Cha bonus of 5 + Spell level 1), which isn't too shabby.
Your Revelation makes your Cha bonus apply to your AC instead of Dex, and adds to your reflex save. You're going to be decently hard to hit, with a +5 bonus to your AC and reflex.
The rest of your abilities, though, cap out at a +1 bonus. So base, you're at a +1 to hit in melee (+0 BAB for starting Oracle), and a +0 for Ranged.
You're getting 4 + 1 skill point per level for the Int bonus, +1 for being human (and possibly an additional one if you do that with your favored class, which I'm assuming is oracle). The rest of your stats are +0.
The Lore mystery will play heavily into your skills. You'll be doing a decent amount of skill rolling outside of combat, and will be able to identify magic items with the best of them. Plus, being able to Brain Drain a captive to get information is just cool.
The Trickier bit is going to be combat. Here are a few suggestions to get you started:
Buff/Debuffer
Okay, so here's where we can branch out a little. My primary suggestion would be (depending on the composition of your party) do something with buffs/debuffs. Bless is a nice 1 min/level spell that gives every ally within 50 ft a +1 attack bonus and a +1 to fear saves. Couple that with your high-ish spell save DC and you could take Bane,Cause Fear, or Doom for a bit of early-on battlefield control. Your High Cha will give you a decent save DC, and additionally your AC will be pretty decent for your class. Also since you can Spontaneously cast Cure Spells whether or not you know them, you're a decent support healer in a fight as well. You can also up your Save DC with Spell Focus in the given school your chosen debuff spell is in.
Fighting Route
If you want to go the route of attacking things youself, I would suggest you take Magic Weapon and Shield of Faith (or Bless if you want to up your attack more, it stacks with the Enhancement bonus of Magic Weapon). You can take feats which make you a bit more effective with your chosen weapon (which, base, is limited to simple weapons), but you need BAB of +1 to get Weapon Focus, and you can't get anything past that without being a fighter.
Summoning Route
Alternatively, you could take Summon Monster I and a few feats to boost the effectiveness of the summon (Augment Summoning and it's prerequisite), to dole out some more damage.
TeeHee you can't hit me
If you want to do nothing but dodge attacks, you could: Take a combination of Entropic Shield, Shield of Faith, and Protection from Evil. Note that the AC bonus of Shield of Faith and Protection from Evil don't stack, since they're both deflection, but you get the idea. Nothing like a 20% miss chance from ranged attacks and a 20 AC at 1st level (+4 from armor, +4 from Cha, +2 from Spell). If you consider upping your Dex to 13 at the cost of say your Con, you could take Dodge as a feat, get another +1 to your AC, and then make up for the loss of a hit point per level with your favored class bonus.
Per your Metamagic Feat suggestion, since you're a spontaneous caster, keep in mind that any metamagic feat you take will force you to spend a full-round action casting the spell. (Aside from Quicken Spell, of course).
Best Answer
Your main hindrance here is the 10 STR. By having all your stats higher than your STR you're saying that melee is the least important thing about your character. And if you're dumping melee, trying to get it back up again via other routes is worse than pointless - decide what you want to concentrate in; many successful oracles focus on the magic and can't hit the broad side of a barn. All characters are about equal when you might need to melee (levels 1-2) and then you could concentrate on the spooky stuff safely. If you really want to melee, then you'll want to rebuild. An oracle doesn't really need that high a INT or WIS (or CON or DEX really). Scavenge those to get at least - at least - 14 STR; that +2 will do more than most other stuff long term. Ta da, +2 to hit and damage that applies to all weapons and stacks with everything.
Then you can take Weapon Focus in your staff, and/or Extra Revelation to get another combat type power. You can also use spells like Divine Favor to bump up your fight too.
If you really want a boost, you can mix in a level of fighter or whatnot as you level. If you planned to do that you might try for some two-weapon fighting feats to make use of the double weapon nature of the staff (if not, forget it; you'll never have enough feats as an oracle to try that).