That is awful, Totoro.
As far as Stats go, Bondo is right, you need a tutor. But that seems to be the least of your problems.
For your parents-- you need to wait and see what happens. If there is physical abuse again, it is best to call a crisis line (not 911, but like a woman's crisis line) and ask for counsel. Otherwise, wait. If physical stuff hasn't happened in so long, a line has been drawn. Something will change. Their relationship may get worse, but what is more likely is that they will both rethink all that was said and done and try to work it out.
Do you have anyone who can help for your movies? Another person who can act last minute? Someone who can loan you a car? Call in favors, ask for favors-- now's the time to ask for help.
It's no wonder you are anxious and depressed and upset. You've got good reason for it. If you can't sleep, watch a movie-- relax. Do what you can to get your mind off of your stresses. More anxious thought won't help you, and if you get your mind off of all this stuff you might be able to think about how you can get out of it. Watch a movie you can laugh at.
And I'll pray for you. It'll help, really.