The last time I innocently chatted up a "taken" woman next to her boyfriend, I was later told by a number of individuals that it seemed like I was hitting on her and it was inappropriate. The allegations totally blew me away because that couldn't have been further from the truth. I was not flirting, I was not touching, I simply asked a lot about her work. I guess old school "bro code" says you shouldn't be too friendly with taken women. Personally, I think it's dumb. Maybe your "perp" thought likewise. And I too would be a little curious why a front-end non-entrepreneur would be at an entrepreneur's conference. Maybe he has some hot new app idea, maybe not.
As for your other examples, though, sorry to hear you had to go through that. With the big-wig, personally, it would come down to how witty of a retort I could come up with, because really, f him. Otherwise, I'd just hold my tongue, which is the safest route, sexist or non-sexist insult alike.