It's just out of the blue it seems. Or is it?? I think he comes around when he sees that I have had enough. Which is just the opposite thing that DBers will tell you to do.
Actually, you probably did some DBing without even knowing it. I've seen a lot of posters talk about their WAS's coming around after the LBS was ready to walk away themselves. In fact, a few months ago I got to a point where I was ready to let my M go. I am also dealing with a long distance piecing situation. I have had career and moving decisions looming without much input or commitment from H and I finally game us both permission to let go and move on, because let's face it, the odds are against people in this kind of situation. I didn't do it out of spite, or just to get a reaction, I really felt (feel) that way. His response was to begin communicating much more and talking about his plans for the future.
I think a gently kick in the butt can be helpful, as long as it is an honest kick, and not to meant to intentionally hurt the other person.
For your H to admit a drinking problem and to attempt to deal with it, is a good thing. Of course, it's just scratching the surface...but some people don't even start scratching.