Do you think the host was tracking everyone’s pizza consumption? Or they should have weighted the split cost based on family members? I’m really not sure what alternative you’re expecting if the cost is going to be split (honestly I don’t like asking how much I owe as the guest OR being asked as the host).
It's very stressful ordering food for a large group if you do it well! When I'm doing it I try to accommodate any dietary needs and be cognizant of different budgets while being as transparent as possible about how it's split up.
Good guests/parties seem understand this and I've never had anyone hesitate to pay me (except one guy who thought there were more people than were actually there and thought I was ripping him off one time).
IMO the real foul was the host didn't try to find gluten free pizza for the wife and I'm kind of annoyed by you for being annoyed by the money and not failure to accommodate your wife