Don't take a passive approach. That's how affairs grow roots and are way hard to get ended. I know. Don't be his doormat. Don't enable his cake-eating. That's what he's doing. It will continue as long as you allow it to continue. Nobody respects a doormat. They pity them, they never respect them. You have to be willing to lose the M to save it. The passive approach never works. You're waiting for him to wise up all by himself and that rarely, if ever, happens.