Help!!! MOTHER ISSUES!!?

I am a 16 year old girl and me and my mother's relationship is on thin ice, most people would say this is normal but I don't think so, not to this extent. It all started when I was about 7, my mother and father both enjoy alcohol and that often lead to fierce arguments, sometimes it even got physical. After my father would leave my mother would often yell at me and call me names and hit me, one time she made me sleep on the floor because she said that I was just like my father though I had did nothing. She even threatened to kill me if my father didn't come and remove me from her house, but my father is almost permanently unemployed so even if he would take me for a few days I always had to come back. Now it's a little different, they no longer speak and she just sits on the computer all day drinking beer and tequila and when she gets drunk everything is my fault once again, and I mean everything, she started screaming at me because my aunt asked her for money, she was mad because she had given money to MY people. One day she was looking for a knife and the knife she wanted was one that I had been using to cut limes, she started going crazy saying that it was strange that I had the knife and how if I wanted to take her out she would kill me first and all this other nonsense. I love my mother and I know she works hard but why am I responsible for everything, what should I do, I'm really beginning to despise her. Oh and while she's on the computer all day it's me and my younger sisters responsibility to clean the house and cook, everything that she should have some part in, we do. Once again what should I do, I don't trust her at all, sometimes I don't even feel safe in this house.