Check out this website.
SunElec.comThey sell many solar panels. I would suggest calling them and asking about 12 volt panels. they have a 21 volt open circuit rating (with nothing connected) and the short circuit amperage is not really the amperage you will get from any panel, because that is the 0 volt amperage. .
I agree that all RV's use about 35 AH to run it for 24 hours. This is about what one of my solar panels puts out in the summer - 120 watt rating. Don't expect that in the winter. . .
Sure you can use the generator, and also run the furnace at the same time. For most heating I would recommend a Olympic Catalytic heater. Get the 8000 Btu if you plan on camping in snow. I have the 6,000 and it keeps my Bounder warm down to about 30F outside, and I want to run the furnace a bit anyway, because it is only the furnace ductwork that heats the basement compartments where the tanks are located.
So I run the furnace about 15 minutes per hour when it is 15F out to keep my 30' Bounder at 70 inside! I have dual pane windows, and pretty good insulation. I pretty much shot off the furnace at night, to save battery and gas, and cover up with blankets. Then when I get up, if I am at -120 Ah or more, I will run the furnace and generator to bring both back to normal.
The furnace can use about 6 amps per hour.
Fred.