Unfortunately the only person who can make him want to be sober is himself. If he was lying about his drinking while you were living together, he'll be even less likely to tell you the truth while three is some distance.
I think you made a very wise decision, but hanging around to try to help means you'll still be enmeshed which will just drag any pain out for longer than a clean break would. I'd suggest following your decision right through and stay away. If he wants help to get sober there is lots out there for him to access.