I wouldn't offer any "help," and I'd suggest a hiatus on discussions about the future for right now. Just keep things low-key, and let him take the lead on what he wants to share with you.
I'd suggest reminding yourself on a more-or-less constant basis that this may not work out. If he doesn't get sober and stay that way, you really don't want to get more involved than you are.
Oh, and incidentally, he isn't "relapsing"--he's just trying to manage his drinking. That never works.