Idk how much propane it takes to heats camper that’s closed up. Ours has a slideout and guzzles propane but it ain’t 100% weather tight.
Consider that driving down the road will be like being in a huge windstorm. But I’d think worst case it’s a bottle a day. Keeping all the water soft will be a function of how much heat and how well insulated and proper circulation.
Pretty easy to test at home since it’ll be winter soon in the Matsu valley. I’d see what you can expect like that first.
Not the end of the world to dry camp yourway down if necessary.