dry camping

An adequate solar system...panels, controller and batteries...determined by an energy survey times 1.5 or 1.75.

Simple answers:

More battery capacity (more, better or newer).

Set thermostat lower so less furnace run time

Start generator when batteries reach 12 VDC under load or 12.2 with batteries at rest.

Solar panels and a back up generator.

furnace pulls lot of power need really good battery to do just one night.

But campground rules often forbid using generators before or after certain times. Some have two 2 hour periods for charging.

don,t use the furnace use a buddy heater OR theres another one that claims its good for rv,s thinks its called camco olimpion. spelling is not right but close.

Install LEDs, conserve power usage, solar, catalytic type heaters, insulate windows.

Get an alternative heat source.
Lil Buddy or something like the Camco Wave heater.
Wave 3
wave 6
Buddy heaters

No fan or battery required, but you do need to provide some ventilation.

Get a Mr Buddy propane heater and connect to your main propane tankes

Buddy heaters or other radiant propane heaters are great, have one myself, but even “ventilation” is not 100% sufficient to keep the moisture down in an enclosed structure.
Those things make a lot of water and a de humidifier is almost a necessity in a camper if one is used regularly.
For comparison, if I heat my 32’ enclosed trailer with the buddy heater (continuously, not just sporadically to warm up for a bit), the little heater will heat up a 250sf structure to room temp at slightly below freezing temps, but if it runs for a day or more without running a box fan and leaving vents open, the walls and ceiling are dripping. With the fan, there’s still a bit of condensation forming. Add the humidity of occupants in a camper and it’s too much moisture.
If in a dry environment and not where we live, it’s better but not a good solution for heating a camper long term.