You could buy a propane heater with a direct exhaust through the RV wall, sucking air for burning and taking exhaust out, no condensation at all. It does not use any current and would supplement your system. If you intend to stay there for a while, I would even think at a wood or pellet stove witch uses a small exhaust duct, the smallest one will heat this rig very fast.
I directed some heat duct from the furnace to the basement water area and doubled insulated everything, even if the doors are insulated, I installed a pink foam to close in the water are. I installed a flapper valve in the duct to close or open as needed. I you do not use the RV furnace, you could install a 12 volt fan in the duct itself to direct air from the main floor to the basement.
A big shade drap can be installed between the front area seat and windows to keep heat in where you live. I also installed some closable heat duct to direct air only in the room or only in the living area and I have doors between the living and room area.
As soon as you have snow, just make a big pile around the RV and on the walls as high as you can, it does protec from the cold quite a bit, the inuit way. Some people are putting an insulated pad or bubble wrap OUTSIDE the RV windshield, it blocks the view but apparantly it is better than from the inside and does not create water on the inside windshield.
12 volt heat pad on the bed actually keeps you warm at very low temps. I will also install a thermostat in the room to keep the room at around 50. This way, the heater will only go on when the room is cold and cut off then it is warm enough.
Have a nice winter
