I've gotten down that low on several trips but don't have any outside hose connections and usually have a heater going inside. Here in Northern Neck Virginia is much the same cold weather wise. ALways warms up the next day.
If you are connected to a house 120VAC 15AMP setup should be ok for the short duration... I would run an electric heater hooked up to one of the THERMO CUBES that activates at 35 degrees and kicks off at 45 degrees (AMAZON). Running the furnace will eat up all your propane and run your batteries down in just a day.
This thermo cube is great for plugging in a drop cord with a 100WATT incandescent bulb in it for heating up the storage area.
I am also setup in my OFF-ROAD POPUP with all my cabinets are connected in my wrap around seating and cabinets on both sides of the trailer. I have installed the small 2-inch round vents (LOWES) between all of the cabinets and have a 6-inch DC axial fan on the shore power cable catch compartment side that pulls air thru the cabinets out the shore power cable hole.. This fan has a thermostat controlled switch which I like to set around 80 degrees for summer months and alot lower for winter months. This works out pretty good for me moving air inside all of the connected cabinets where water lines are located etc...
We use the BLOW OUT method using my 12VDC tankless air compressor connected to the city water port using an adapter when camping in the cold months. Can drain the fresh water and blow out the lines pretty quick when needed. Then just add some pink stuff to the P-traps. When it warms up the next day we just add fresh water and continue on...
Everyone has different approaches but this works pretty good for me for my smaller POPUP footprint.
Roy Ken