I did do the microwave test today. The batteries were fully charged at 13.2 volts. The sun was out so I was able to pull the trailer out and turn on the Solar.
The solar charge controller started charging the Bats at 14.6 volts but since the batteries were already fully charged it dropped to 1.2 volts in a few minutes.
I turned on the Inverter and connected the trailer to the inverter. Turned on Microwave voltage dropped to 11.74 for the first 30 seconds then slowly went up to 11.83 for the next 3 minutes and the Microwave timer shut down. IT WAS AWESOME! Worked great. Solar Charge controller charger was at 10.5 volts but slowly dropped down to a trickle so I don't think there was much of a draw on the battery bank.
We only use the Microwave to heating coffee or thawing something for a couple of minutes so, this will work out great.
The test may have been aided by the Solar but not sure if it works that fast. I think removing that switch from the Inverter power cable must have made a significant improvement.