Before losing another minute of sleep, go down to the nearest HF and get one of their clamp-on ammeters (also reads voltage) - currently $11.99. Also get a plug-in digital voltmeter like in the 2nd pic so you can routinely keep an eye on the voltage - under $10 Amazon or ebay. Will need to open the panel to read the current on the 20 amp (AC unit) and 30 amp circuits. I would also measure the voltage right at the AC unit and in addition would take some readings at receptacles to see if any voltage drop is limited to only the AC unit circuit.
If the AC unit will run for long periods of time and the 20 amp breaker in the panel does not trip, the AC is not drawing extremely high abnormal current. When the 30 amp breaker trips, does it trip instantly or take a second or two?
While the AC unit *could* be drawing abnormally high running current (say 15-25 amps) there could also be a poor connection(s) somewhere between the pedestal and converter panel and/or the 20 amp AC unit circuit. Maybe when the MW is turned on, the additional current draw worsens an already low voltage condition due to a bad connection which in turn causes the AC unit to draw even more current?? With the AC on, what would happen if you plug in say a 1500 watt hair dryer? And with the AC off, what would happen if you plugged in an electric heater (for testing only) and hair dryer to create a resistive load of 3,000 watts and then turned on the microwave? The 30 amp breaker should not trip but if it does, then that would indicate a bad connection somewhere. Extremely unlikely to be the new 30 amp breaker.
If you do have a bad connection(s) somewhere, you need to fix it asap as it's a potential fire hazard. In our converter panel, I recently found one 15 amp breaker that had a completely loose wire at the breaker's terminal. Factory wiring is often substandard on both 120VAC and 12VDC wiring.
Good luck and whatever you find the cause of the issue to be, please post your findings.
