Congrats on getting started with your first game. It sounds like have an excellent story going. I'll ignore the story-specific elements of your post, and focus on the question, "How can I handle being in a party where my character is at odds with everyone else?"
First of all, you should determine whether this is purely a conflict between characters, or if it is having a negative effect on the table. Think about the other players - are they having fun? Do they enjoy this kind of play?
If Your Group is Enjoying It
If the other players are enjoying this, then you are in good shape! Keep it up, have fun with your character and their backstory. You can expert a certain amount of conflict between the characters, but if you ever suspect that the other players aren't enjoying the conflict - see the next options.
If the Group isn't Enjoying It
On the other hand, the rest of your group may not be having a good time. Maybe they don't enjoy this kind of game, or maybe something about your approach is too aggressive. But for whatever reason, it's dragging down the game.
At this point, think about whether the other players have a problem with your character or you.
It's a Problem With My Character
Congrats, you have succumbed to My Guy Syndrome - a seldom fatal condition where a character is a huge downer, and the player justifies it because that's "what my guy would do".
Maybe your character can be rehabilitated. He takes a new oath, has a revelation, is psychically possessed by a new mind, has a new soul implanted - whatever. Maybe you talk to the other players and change, with no in-story reason. In any case, you decide to keep the character, but try to make him more acceptable to the other players.
If your character is beyond redemption (or if the situation is dire enough that the other players don't buy it), consider killing off the character and starting fresh. With the next character, setup a backstory that is less adversarial.
It's a Problem with Me
This isn't described in the question, but it is possible that the other players don't like you. In-character conflict is sometimes a proxy for conflict between people. If you suspect that is happening, talk to the other players and see if it can be resolved. If it can't, it's probably best to leave the game.
The flask is saved for when the DM asks you "do you have any glass containers" when you are trying to harvest a blood, poison or venom from vanquished monster.
People then try frantically to calculate how many health potions they have drank recently to convince the DM they have a lot of glassware that can be used to contain the valuable ingredients.
RAW there is no info on that - the bottle does not magically vanish. You end up with an "empty health potion flask" you can do as you wish. If you don't really note it down it can be assumed you just threw it away. If you do - you have put it in your backpack.
Best Answer
If you're a mythic character, then Recuperation gives you a full night's rest in 1 hour, including refreshing daily abilities such as spells. You can do this multiple times per day, limited only by your mythic power points. The item Cornucopia of Plenty makes this more power-efficient, but still requires a mythic character.