My goodness, I am so sorry to read all this. How tough it must be.
I would recommend you reading some books by Alice Miller. She is a psychologist who writes about relationships with parents with a focus on abuse issues.
It may not seem abusive because it isn't intentional, but the way your mother is treating you and forcing you to act the adult is abusive regardless.
I empathize with you; my mother would try to suck me into her world like yours, and I couldn't stand it. Sometimes I would ask myself, "If I just knew her as a person, not as my mother, would I put up with her behavior?"
No way.
But then she is your mother...
It's hard.
I hope you do some reading, and perhaps get some counseling. I know on most college campuses they offer free mental health assistance.
Best wishes!