Go with a small oil filled and small gen. I about went broke last year buying propane to heat a 26 ft trailer. WE were using a 20 pound tank a day. went to town and got a oil filled radiator problem solved, only used a couple of gal of gas per day and kept the trailer at 70.
I used a buddy heater last year, and had the same issue with dampness, ice on the insides of the windows, etc.
Fireball, I know you said no electricity, but this year I'm going to try a small genny, a 50' extension cord, and a ceramic heater, or maybe a oil filled portable radiator, or both. I don't mind cold, but I hate damp.
PS: +1 on the CO detector.