I'm an actor and director in the theatre scene here. In twenty years of doing this I've encountered two types of people who audition for stuff: those who want to GET the part, and those who want to PLAY the part.
Those who want to GET the part just get off on the high of winning, of beating other actors to the role, and that's where the effort ends.
Those who want to PLAY the part are grateful for the opportunity and work their tails off to explore, stretch, and play the role to the best of their ability, from the first rehearsal to the last performance.
Your ex just wants the high of winning. He doesn't want to do the actual work of a relationship. You're going to have to be the one to get off the merry-go-round here if you ever want peace and the real happiness of a healthy relationship.