Ok, so those settings may have been incorrect, but that's not causing a breaker trip. There's still something else going on. Can you run a heavy extension cord (12 gauge) from an outlet in your garage directly to the plug/cord on your microwave? (Don't use a cheap cord, it could melt.) If the microwave works that way, there's a problem in your trailer, either a wiring fault or a bad breaker in the Xantrex. If the microwave trips your garage breaker, there's a problem with the microwave and it should be replaced.