You already have the solution. One A/c unit. Run the frige on gas. Turn the A/C off when operating the microwave.
Not much else you can do. Also. Be sure to monitor the voltage. Running a motor on low voltage will do damage over time.
Ideally you would have a whole house electrical management system that would shut down the power should the voltage drop below, as I recall, 108 volts. I might be remembering wrong on the 108 number, but the rule of thumb for safe operation is 120 volts +- 10%.
Enjoy Sebastian. We lived in Fort Pierce for years and have camped there often.
