Great post and very helpful!

A couple of quick notes --
1) based on my Sept experience
757 p.s. (3-class): 2 in Y, 1 in C, 0 in F is incorrect, it's:
757 p.s. (3-class): 1 in Y, 2 in C, 0 in F

2) carry-on restrictions: we always fly with a rolling tote/briefcase in addition to the pet carrier. I would say that the carrier is considered your "personal item" rather than your carry-on item.

3) I didn't see mention of the health certificate requirement. This is one of the more expensive aspects of flying with a pet (my vet charges $77 for this). UA asks for it about 20% of the time at check-in.