Cats -
First of all, you have to stop trying to "understand" and "figure out" alcoholism. My abf is amazed at how I, an RN can't "get" addiction. I've finally gotten to an understanding that all I will ever "get" is this: I am a logical person. Addiction is not logical. Addicts are not logical. The most I will ever understand is that I will never understand addiction.
That's it. I understand that I don't understand and that's the best I can do. Trying to fiugre out how far gone your H's addiction is or if there is hope for him to get better or if you should stay or go........none of those can be answered by anybody but you.
You have to decide what your boundaries are (what you are and are not willing to live with). Once you have decided that.........he will show you if you can or can't stay with him based on how his behaviour does or doesn't line up with your boundaries.
I strongly encourage you to find a local alanon meeting. We nurses are strongly wired towards codie-behavior as it is.......get there and learn and be strengthened/encouraged by those who have been and are where you currently find yourself.