Ange, I will echo the recommendations of others, and suggest you contact Al-Anon as soon as possible.
Your father’s drinking problem and your parents’ marriage problems are not problems for you to take on. You are responsible only for your actions, not for your parents (either one of them).
I don’t know enough about the specifics of the situation to give good advice. But based on my intuition, and having been in a family where both parents had drinking problems, I’d recommend you run, don’t walk, to get out of this situation. You’re 27 years old, and you’ve had to deal with a fairly dysfunctional family situation for a long, long time (if not your entire life).
Your mom will have to make her own decision to stay or leave, based on her own reasons. I understand your desire to help, and if your mom decides to leave, if and when the situation comes to that, then you can offer your help. But it’s not appropriate for you to influence her decision, one way or the other.
Please keep in mind that excessive distance or closeness can be a sign of a dysfunctional relationship. Co-dependency is a very strange and entangling situation, but it can be overcome.
Good luck!