I am so sorry to hear about your familys trouble!
I had a father who would do similar things and it was so tough to grow up and not be able to do anything!
And it's not just that he drinks and acts like an idiot, it is also the fact that your mother acts like one and doesn't stand up to him. It is so tragic! I wish I could help you in some way - but all I can do from here is tell you that your local Al-Anon might be able to help you - call them and get someone to talk to about this please!
My biggest fear when I grew into my 20's was that I was going to be a woman like my mom and not stand up for myself or my kids. Luckily I didn't, but that has cost a LOT of hard work with myself. But it can be done
Go stand up for yourself and get help my friend!
EDIT: I just read the former posts thougroughly (sp?) and I do not agree that you should take care of your mother and be extra helpful. She is a victim because she chooses to be one instead of getting up and getting out. Your mom is NOT your responsibility, you are hers and she is a grown woman who should take care of her children and not teach them to put up with abuse.
You just take care of yourself - you have a whole life ahead of you and can still choose not to follow in your parents footsteps...