Hi Beth,
Both of my parents are now dead, but I experienced many of the same feelings you are when they were still living. In my case, the n was my father and the enabler was my mother (although she certainly had n traits). My father was an alcoholic, emotionally abusive bully to everyone in the household, including my mother. But like your mom, my mother saw him as the leader of the houshold and she would not/could not make a decision unless he was in agreement.
I became a much stronger woman than my mother ever was and could eventually stand up to my dad--on both her behalf and mine. He and I had more knock down, drag out fights than I could count. For many years, I maintained the relationship with them, because of her. What eventually made me turn away from both of them was her constant support of his bad behavior and taking his side even when I was trying to protect her. Also, I did not think it was healthy to subject my children to the constant fighting that went on when we visited.
After he died, all I heard from her was what a great guy he had been and such a wonderful husband and father. It made me want to gag. But in some twisted way, I think she needed to justify in her own mind (which at that time, unknown to my brother and I, was beginning to suffer from Alzheimer's) that she stayed with that jerk for over 50 years.
I found that I was never able to truly forgive her for not supporting me and even when she was very sick with her disease, I rarely had any contact. I probably should feel some guilt about that, but I really don't and have not missed either of them since they died.
I know that feeling of dread at having to visit and spend time in their presence. Sadly, it does not go away unless there are changes. They are probably never going to change, and it will be up to you, Beth, to make the situation livable for you. The only thing that worked for me was to completely disengage, but perhaps you can find a less drastic approach. I wish you well.
Hugs,
Brigid