Wellcome to SR.
I will not write much as you have already been told so many wise things, I'll just tell you I understand how you feel. My STBXAH (soon to be ex alcoholic husband) is in the same condition as yours. I stood by him for years, thinking I'm his only hope for better, healtier life. In May he was admitted to hospital with cirrhosis, end stage, stayed alive against all the odds, stayed sober for few months and than started drinking again. You can imagine the effect this had on kids and me. Yet I stayed for awhile longer, until I understood he was making me go crazy literaly, I could see he was drinking but he was convincing me he was not, and I thought I was imagining things. I ended up seeing a shrink and was put on AD. We lived like that for few months, him getting more and more drunk every day, coming home wasted, his pants pooped, unable to walk, the lot. Than I discovered he has a girlfriend and that he cheated on me for years. Upon finding that out I was free of guilt, and finally able to say goodby to him. He moved out a month ago, and my life was never better. Kids seem happy too.
Still sometimes I worry about what will happen to him, will he die alone, but I know that is the choice he made, as hard as it is for me to accept it.
As FD said, for me too most important thing to realize was I did everything I could for him, and if I don't do something for myself and our kids he'll destroy us too. That is what made it possible for me to leave. I had to save our kids and myself. It wasn't easy, but it was better than the alternative. I found him a flat and I'm paying rent for it, I'm paying his medical insurance. Still I'd do anything for him that doesn't jeperdise my well being or the well being of our kids.
I speak to him on the phone, but I'm trying to do that as less as possible, as each day passes by I'm realizing more and more how much he has damaged me, and how easy it is for him to manipulate me and pull me back into the madness of his life.
I don't know how am I going to feel once he is gone. I know it will be hard, but it the same time I am confident I'll remember there is nothing I could have done about it.
We don't own anyone's life or death but our own. We don't owe anything to anyone but to ourselves. I believe we were all given this life to make the most of it. We are not put on this earth to nurse someone who doesn't want to live. As if we keep doing that, we keep losing ourselves and distancing ourselves from the only purpose we have in this life, which is IMO to be complete, healthy, good, grateful human beings. Life in misery is life wasted. And more than anything else, I believe I'm teaching my kids by example and it is my job to teach them how to take care of themselves and how to be happy.
None of it is easy but life's beauty comes in all way, shape and forms. Sometimes we can even see it through tromendous pain.
You can't save anyone but yourself.
I wish you well.