I can't pull them up right now, but I've read a few really good articles recommended by people here about what happens to an alcoholic's brain when they become alcoholics. At first, they made me furious because I felt they sort of "excused" why someone I gave up everything for could spit me in the face and tell me I was worth s***. But then I realized that it actually helped me to think of it as him not being the same person I fell in love with. Accepting that that person was gone. As much as if his body had been taken over by body snatchers.
I can relate to your sense of utter betrayal and disbelief. And your beating yourself up. It sounds like a backwards thing to say, but I think it's a good thing that you've come to the place where you know there's no going back. I think all those years of hoping and seeing your hope thwarted are much worse than the purgatorio of getting out of an alcoholic marriage. At least that's my experience. And I wish you strength, love, and supportive surroundings during that journey. Just remember that you will come out on the other side, even if it doesn't feel like it every day.