First quit seeing this guy who might've sexually assaulted you. Even though it's a might, it still seems pretty scarey. What if the the "might" became a reality? Don't even give that a chance to happen.
Second I think you should just be there and be supportive of your dad. I'm guessing he's stressed and has a very short temper. I know it's hard to deal with, especially when he blows up at you for it. Try to put up with it though. In the end, he'll really thank you for being there for him.
Also I'd try to do anything I could. I know family can't testify for family, but see if you know anyone who could testify saying he absolutely did not, could not touch another girl. Don't try to make it all big, as your dad will just tell you that it is adult business to deal with. Just get the gear in your head turning. See what you can do.
As for the medicine... those are steroids aren't they? Or one of them is at least. As long as you don't want to become essentially a man, stop it. Also you shouldn't put your liver through that much strain. You're gonna need that someday to manage your blood levels and you already need that to metabolize fat and lipids. unless you want to have that pot belly, weird jiggly shaped front thing, I think you should stop.
I know it sucks. It really really sucks. I've pussied out and drank and cut before. But you gotta hang in there. Maybe trying to help your dad will keep your mind working. You might tell a friend. Try to keep yourself busy. I know it's hard to stay positive. Just don't be negative. Don't give up.
Also... you may get a job. Anything that would help. Even things like babysitting. If you worked at a fast food place you'd need to drive there and back everyday. I don't know how much that would hurt the pocket book with gas money. But see what you can do. You can also take shorter showers, conserve energy, turn off lights when you're not using them, probably turn off your computer when you're not using it, don't talk on the phone as much, don't use as much heating - just bundle up at home instead (it's really quit comforting and cozy to do that), see if you can do the laundry in less loads.
Just try everythign you can to help and keep yourself busy.
And don't talk to that guy anymore! you don't even want any hopes of dating him if he's goign to sexually assult you.
So keep hangin' in there. Good Luck