OP, you are right about rating. We didn't check that, that is where companies cut corners, but we didn't have a problem towing 3 horses 13 hours, just when we bought a horse at an event and were towing FOUR horses on the way back. We had already put a lot of miles on this trailer.
Seriously, though, you need a spare tire. You never know when you will pick up a nail or something in a construction area and blow a tire. AAA doesn't have the resources to help you with this, although I'm thinking about switching over the you S Rider.