I would be really put off by someone asking me why I'm not married. Its super rude, even just of an oblivious ignorant kind. I also think some of the things he's said to you in conversation are odd and contradictory. Its understandable that you are put off. Whether or not to continue the communication, is up to you. Question though, why do you want to continue friendship with him despite this strange off putting conversation if you guys aren't close? Like what's the decision based on for you?
In terms of your speculation, I really don't know and you may never really know either. I think the main important thing is that he's off-putting to you, and you don't have to continue a friendship if you don't want to.