They say that alcoholism is a family disease. The alcoholic and the spouse are in a dance which is sometimes codependent or abusive, but which is always filled with denial. The spouse is damaged by the relationship and so the children...and then the children pass that damage on to the next generation. When you talk about your alcoholic father and codependent mother, you've got to remember that they were very likely damaged individuals coming into that relationship.
Children are survivors. They do what ever it takes to survive. Those codependent behaviors are learned as a path to survival in their childhood. But it's a strategy that then often fails them in their adulthood. Your codependent mother didn't get that way on her own. She didn't choose to be codependent. It's a survival strategy, codependency chose her.
Unless she's aware of her codependent behaviors and how they are hurting her and those around her, she can't choose to change her behaviors. She's simply not aware. Often we hang onto our behaviors, no matter how dysfunctional they may appear to outsiders, until they fail utterly and completely. In Al-Anon we say: "We admitted that we were powerless over alcohol and that our lives had become unmanageable." We usually only reach that point when our lives have reached such a low place that we're finally willing to admit that the way we are living isn't working.
That's when we are capable of choosing another path. That's when we can choose a spiritual path that can free us from bondage. Your mother is 70 years old. She seems stuck in her old behaviors. They work for her. She may never change.
She's not your problem.
Your problem is how you react to your mother. She's going to do what she's going to do and you're powerless to change her. The only person who can change your mother is your mother.
The only person who can change you is you.
I read today that "therapy" begins when the patient gets tired of listening to their own stories. You're clinging to stories about your childhood, about your mother and all they are is stories. They inform who you are right now, but they don't put any limits on who you can become. Change is possible, it takes courage and wisdom...but I truly believe that change is born of desperation. Only when we're sick and tired of the way we are, are we finally ready to look for a new way of being.