[Phalanx]

Ha, I don't even consider my family, family...

1- What can I do to help out my mom?

Try having some 18 year old friends smack your brother around some.
Do the dishes.
Don't make more mess than you're prepared to clean up, promptly.
Throw in on the occasional bill/grocery shop.
...I think that should have you covered.

2- Should I push myself to move out, or to stay for as long as possible?

You should discuss this with your mother, frankly, without any "I am a parent and therefore required to give certain answers" bullshit coming into it.
Be adult about it. Discuss a plan on what you both come up with on level ground.

3- What do I do about sleeping on a couch?

I don't mind sleeping on the couch...as long as you've got a level surface and your pride isn't above it, a couch is fine - we used to sleep on hay, dirt, rocks and the like...some still do.
I think it's a perspective thing.

4- Should I get my GED so I can work more. The GED will give me enough credits for my deploma.

Work is just work...if you need to, put in any additional effort to get the kind of work that makes you financially stable and not want to kill everyone around you, that's about as good as it gets.

5- Is there anything you can suggest to relieve some stress?

Weed, screaming at night, excersize, jasmine tea, listen to the rain when it's available, Touch your fingers and thumbs together, close your eyes and focus on only the sound of your breathing, and the pulse you feel through your fingertips - that one's my personal relaxer.

6- And is there any new movies that you would recommend? Just a-wonderin'!
Might help me unwind... Usually does anyhow!

Try old movies that you've yet to see. Almost definitely gonna be a better way to spend your time.