You're not a "prude." I wouldn't have made it past the front door. But besides that foolishness I really hope you're not seeing this guy anymore. He seems entirely useless. I don't know you, but you're a person and therefore deserve better.
The only thing I wish you had done that you didn't do here is tell that girl who was suggesting her boyfriend to you that Max had brought you there more or less by force. Honestly, he knew it wasn't your thing and was happy to put you in a just really uncomfortable situation and mess up whatever it was you had with him... I don't really understand after that why you felt you needed to be supportive and not embarrass him. Let his friends know he doesn't respect boundaries.
Probably you were his ticket into that event and that he brought you there basically against your will means he was willing to lie to you and his sex buddies about his motives and respect for consent. It would have been great if you could have screwed him out of parties with that group after his little stunt.