What to do in this case?

I feel like you should just back off. He is married. I don't know about you but I don't know too many people who want to get involved with someone who is married and know they ruined a relationship let alone grab on to that baggage. Why would you want to be with someone who is willing to go meet up with someone else when they are married. Even if they did leave wife or husband...wouldn't they maybe do the same thing to you? Or maybe you want an open relationship. Still just sketchy and really sad. But do what you feel is right...