I too lived with alcoholism in my family (my mom, my aunt, two of my grandparents), and you're right -- it's a tough call.
I do know that they have to "hit bottom," or at least WANT to do something about their drinking.
I also know that sometimes interventions do work, and I also know that you have to, at least, first separate the addict from the source of their addiction (get the alcohol out of the house).
I guess my own belief in a way around this chicken-and-the-egg thing is to help "prime the pump." I do believe that someone in a life crisis is far more likely to make a move back toward the marriage, if the OP is out of the picture. Can we totally control that? No. But there are things I believe we can do to make it a helluva lot harder for them to continue it, and if that helps "prime the pump" to start their recovery, then I put it in the "hey, whatever it takes" category myself.
