Welcome to iRV2.
I just left for the south and don't envy anyone staying in Canada this winter ; weather already getting way too cold. Winter of 68 comes to mind , 93 was bad too. Even in the southern, and coastal, B.C, areas
Back to the question at hand , find your water pump , and hang a 40 watt trouble light bulb ( regular bulb ; not LED ) close to it , this will help with temp in the bay with the tanks when the furnace is not cycling. If you have an outside shower , insulate around it. Pack steel wool around the plumbing where it exits the coach and then insulation over top, even if your skirting the coach to the ground.
Note be prepared to run in the slides and hunker down if the weather gets nasty ; slides are the insulation weak points in any RV.
Stay warm and safe .