Pretty sure he thought he wants to do erotic stuff before getting married. エロリ事がしたい。。。あと結婚. あと means "afterwards" in this situation, no?
More literally, I think this would go like, "I want to do erotic stuff, and then what's left is marriage".
I may be mistaken, but if he meant marriage comes first, he'd think 結婚のあと.