First, is the undercarriage (area under floor and between frame rails) enclosed? If so, is it heated by a furnace duct?
Don't know what trailer you have or the access to the tanks/location of tanks. Some source of heat (space heater/100 watt bulb) can really help some to keep areas warm.
Certainly AF in the tanks should help--hope you are using non-toxic stuff?
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired