Which model do you have - the 73536i (yellow w/black lettering) or the 73540i (black w/yellow lettering)? I have the 73540i and it sounds like you have the 73536i. They are essentially the same though it looks like the breaker on yours is a simple push to reset button under the receptacles and mine is a toggle switch with on/off.
I will say that I don't run the microwave much when using the generator, but I do test it periodically by heating some water for cocoa or some leftovers. It does the job, but it is definitely working hard. If you haven't tried it yet, perhaps flip it out of "ECON" mode. Fuel consumption will go up but it may run a little better under heavy load that way.
TT: 2015 Jay Flight SLX 195RB Baja Edition
TV: 2014 RAM 1500 Bighorn CC, 5.7L Hemi, 3.21, Factory Air Suspension/Tow Pkg, Andersen WD/SC