Basic electrical theory....
Volts x Amps = watts. So...
Since the trailer nominally runs on 120 volts and the main breaker is 30 amps....
120 volts x 30 amps = 3600 watts.....i.e. any generator over 3600 watts is more than the main breaker will let through before tripping.
The starting draw of the A/C(1200-1600 w), along with the draw of the microwave(800-1300w) and the water heater(800-1300w) will most likely exceed 3600 watts and trip the main breaker even on shore power. Not to mention, the 12v converter can draw up to 800 watts off the 120v system if you are using a lot of 12 volt power.
These numbers are theoretical, so it may run all three, but I'll bet you'll have a real hot plug. Like melted hot, been there, done that, replaced the plug.
So, If you are boondocking, run everything you can on propane!!