For starters, I'm surprised know one has mentioned needing a good sized battery bank. I would start with 4- 6 volts. If you do not need air, get a Honda 2000 (3000 if you need air) and you should only have to run it maybe 2-3 hours a day if that to keep the batteries charged up. Run the fridge and water heater (only when necessary) on propane. We can boondock several weeks at a time on one 30lb lp tank and 5 gallons of gas.
Do not use the on board genny ( as you found out they really suck up propane) and keep a watchful eye on the 12 volt things you use like lights. Do not leave anything on that is not necessary. Use a propane grill for most of your cooking needs.
2018 Chevy 3500 LTZ Dually Diesel 4x4 CCLB
2011 Montana 3455 SA. 6 point level up. Disc brakes. Curt Q24 Hitch
Progressive EMS. Valterra tank valves. Sailun G637 tires. ARP fridge control. All led lighting. Mor Ryde IS
If you want to run 1 a/c once in a while then you could install an easy start from Micro-Air on your a/c and then you could use a Honda 2200 watt or equal Invertor generator. The price is 299.00 for an easy start.