Separation really is the best. I was in a similar situation to you when I was younger, OP, and I ended up getting my custody switched. That also sucked. Now I live alone, but across the street from my mother and step-father and sisters, and next door to my father. Though my father is still tolerable only in low doses, I have a great relationship with everyone now.

One point I disagree with >>2 on is calling the police. It's one thing if it's real pain, as in, full beatings, but by now, you're what, 17, 18? There's doubtfully a real threat... If you think there is one, or if you have younger siblings that she's being abusive to, though, call the cops, or go stay with a friend or something.

Most teenagers go through this. It's not too late for anything, just go with it, finish off the bullshit that is highschool, and get out of there. By your early to mid 20's, you'll either have realized that some of your actions were wrong, or some of your mother's actions were wrong, or probably a little of both. Don't worry about anything, answers and improvement will come, and very soon for that matter.