Hello Scrapiron,
I have heard the phrase "some alcoholics just grow out of their drinking." I don't know whether that's true or not regarding drinking, but it could be true for volatile relationships such as yours. Is it possible that you have actually matured over time? One would hope so.
I look back at my life, my early adulthood, even middle adulthood, and I just shake my head at some of the things I did then. I say to myself, "What were you thinking???" I find I am more compassionate as a result when I see people behaving as if they have lost all sense. Perhaps you have somehow gained some sense over the years.
I also think that some souls simply have some karma to work out between them while they're here. Maybe they get it done in this life. Maybe they don't and take things into the next. It's the only way I can wrap my head around why two people who have a tortured relationship for DECADES would still keep at it. I have to just think, sometimes, they're meant to, they're working something out from a long long time ago. All the advice in the world won't make them re-set their course.
Being around alcoholics is not good for our bodies (aside from our minds). It's good you are running. (Which might be symbolic as well).