That is a lot of propane. How big is the RV?
I would check the ducting to verify the heat is all getting to the living space and not lost to some compartment or to the exterior. Unfortunately much could be hidden so check the volume of air. Yes if it will be close to freezing or below we run a space heater continuous to supplement the furnace.
If there is a leak the most likely place is the regulator. If it is over 5 years old it would be OK to just replace it. Also the regulator should switch cylinders automatic so there is no waking up freezing and running outside to change cylinders. Check the indicator and fill every day if needed during a cold spot.
I prefer the Cavagna brand regulator.
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