If he talks about marriage after sex?

Get married and stay married. Yes he obviously does want to marry you especially if he talks about kids. But it depends on who the guy is and all the factors that surrounds your relationship.

It's hard to say. He might still be high on the sex right afterward. Sex can do that.
But at least the thought in in his head. Whether or not he follows up with it is yet to be determined. . But if he brings it up at a non-sex moment, then you may have something there.

Probably means you busted his cherry, or he is not really experienced, sorry to dis your man, at least its better then him taking off in the middle of the night and asking for his socks back or to loan him money, or there is something else he could leave you with that he's not going claim

Definitely a hint that he's at least sorta into you! But I wouldn't jump to conclusions because that's just ALWAYS dangerous to do.