First Time Boondocking.....Need a few Questions Answered

first get rid of the single 12 volt battery and go with 2-6 volts trojan T-105 batteries wired in series and you won't have any problems with heating and battery usage as far as propane usage you should not have a problem as i can go 14 days on 2 30 pound tanks and using the heater every night just make sure the batteries are charged up before you turn in for the night also for good reading do a search for the 12 volt side of life part 1 and part 2 on the web tells you everything you need to know about batteries