I mean, from what I understand of the path, the big bad is at least a devil of some kind, so having a shitty party makes some sense there (since a devil is essentially the worst boss you've ever had, but with all the worst bits turned malignant and cancerous). But why the hell would a noblewoman decide to help you based on whether or not you know how to eat oysters properly?
He's part of the ruling family of the country of Cheliax, who made a deal with Devils in return for a ton of power. Again, no idea what the points are for here. Maybe to influence the nobles that were attending? I don't know what I can or can't mention about this banquet without it being spoiler-territory. The only free-roaming is done by a no-name NPC from your rebellion who manages to sneak in as a guard, and help out a tiny bit. The DM allowed our Rogue to do this instead, as the NPC was several levels lower than we were, and wouldn't actually be able to help. But if a player poses as a guard, they can't do any eating or dancing or mingling.
The noble-woman already likes the rebellion, but believes that a rebellion should be led by those with tact and grace, and if the players don't demonstrate that, she'll step in to lead the rebellion herself.
The Problem-Player comes up a lot in this topic. Always the asshole meta-min-maxed, super optimized, who's just "doing what their character would do" while trying to dominate the game and stand in the spotlight, or fulfilling a power-fantasy if they are the DM, with a meta-min-maxed, super optimized DMPC, who's just "doing what their character would do" while trying to dominate the game and stand in the spotlight.