I am assume a lot off of your post like you will have hook ups and you have a 4 season rig.
The tanks are heated by the furnace, so use the electric heat to augment but that furnace has to run to keep you from freezing up. Just in case, I would add some anti-freeze to the waste tanks. Also remember the sewer hose isn't heated, will freeze up and may break, so don't leave the gray water valve open.
You mentioned not leaving the hose connected because it may freeze, I'd have water in the fresh water tank for a few reasons. First, the whole system can go down to freezing up. Second, with the tap hooked up, if a line in your rig freezes and breaks, the water will just keep coming. Using the tank means you can shut down the pump and if a break happens, you won't have a flooded rig. You can get a heated hose for the tap but I still suggest shutting it off when you dont need it or at least while you are away.
Open the cabinet doors and drawers where the plumbing runs behind them. No heat is usually forced into those areas and they can get mighty cold.
The fridge is fine down to 20 degrees, below that and it will stop cooling. Putting a 100w light bulb in the compartment will keep it warm enough to keep going.
We put heavy bath towels over our windows on cold nights. It really cuts down on the heat loss. Rugs on the floor help too as do inserts for the vents. Those are just thin plastic and you can really feel the cold dropping from them.
The stove and oven are propane and are not vented, so make sure you vent while using them.
The last things are make sure your propane tank is full and you have a means of charging up the battery if the electric fails.
These are basis things, there are more if you would be doing it a lot or for extended periods of time.