Hi,
It is entirely possible to be warm in a class C. I've done so down to -37c (-34 f). You need enough battery bank to operate the furnace and enough propane.
I've managed to modify my unit so that it requires about 19000 btu's to stay warm. Window covers made from insulbright fabric are quite useful.
One of the issues of travel is that the furnace gets "fooled" by the dash heat and won't cycle enough to keep the fresh water system thawed. I replace the cold air return grill with dual window fans and that solved the issue for me.
I've made mods to allow me to heat 100% electrically. It does take a peak of 6000 watts to do so. I got around the limitations of the 30 amp shore power cord by adding two auxilary cords. One 20 and one 15 amps.
It behooves you to protect the fridge at low temperatures. It can freeze and fail when operating. The damage is progressive.