More information is needed to answer your questions. The most important is what converter/charger do you have now, and how many of what kind of battery/ies?
I too use a Honda 2000, with my microwave, 55 amp three stage charger and A/C. I can run the charger the same time as the microwave or A/C, unless the batteries are exceptionally low. I cannot run the microwave and A/C at the same time.
On the microwave, years ago (about 2005), I purchased a counter microwave from Best Buy for $40, and it had a $40 rebate. So, it was free. I pulled the outer sheet metal off, about 8 screws, and fastened two pieces of aluminum angle to the outer sheet metal. One piece holds the microwave to an overhead cabinet, and the other holds to the closet.