I think you might be surprised once you leave at how much of his "functioning" is you propping him up. These guys are way too in love with booze to want to take on more than a bare minimum of parental or personal responsibility. My ex can't even take care of dogs, cats or himself. As soon as I left he quit his job and has basically been on an eight month bender. He hardly even talks to our son on the phone.
Before I left I might have described him as functional. Not anymore.