I am fairly new, but welcome, every hurdle is success.
I don't know much about not being a drinker, I know less about giving up the drink...... but I know a WHOLE lot about human to human relations, I as a under profession write human resource contracts, some are still being used after 15 years. One thing i learned early in to my part time career was that humans have choices after singing the dotted line, and even after a contract corrects them, chances are they will do it again, I am sorry.
In my opinion if you want a non-drinking partner, this person is not the one. paying the difference of the lease to ensure you are not responsible would be easier than asking him to pay it, cause that is the only real concern involving you moving on that I saw.
P.S. you can love your EX's, as long as you take care of yourself first.