Show me - How long is a piece of string??? I am the alcoholic mother which you have so vividly described. I blamed my daughter's father, my ex-husband, for my drinking, blamed him for committing adultery - (Who wouldn't have, with a drunk of a wife to come home to??)
My eldest daughter left my home at the age of 15, but now 10 years on, and me in recovery, she is living with me again, and we have a wonderful relationship. I hope that one day your mum will find help for herself, and then you will see the real mother who is hidden beneath the alcohol. Until then, I believe you are right in stepping back, since it is affecting you so badly. I am also the child of an alcoholic mother, but forunately, I was sober before she died, 13 years ago, and was able to have a year of a good mother/daughter relationship. My mum never did get any quality sobriety, but she was so pleased that I had done, and oddly enough, for the last year of her life, due to terminal cancer, she didn't drink either.
Keep on doing the right thing for you and your supportive family and friends, and pray that one day your mum will get help.