Well, the good news is that it looks like, on some level, he's aware of his problem and wishes he didn't have it. On the other hand, it could be a very long time before he's ready to do the work necessary to live a sober life. You aren't obligated to stick around and wait for it to drop, though.
What makes you think he'd kill himself if you left him? Is that something he told you, or something you concluded on your own?