Will my tank freeze?

Simple answer to your tanks freezing, YES

I've done deer camp in North Dakota.

First thing to freeze, will be the dump valve.

I have the electric heat pads, with enclosed underbelly and heat duct into the tank area. My warm holding tanks are useless when I can't dump.

What I have done, when hitting the road, I put disposable pocket warmers inside the dump cap. When I get back to town, the dump valve is usually thawed enough to dump.

For traps and water lines, I leave cabinet doors open, to allow heat to get under sinks, etc.

Another thing you might consider: put a gallon (or two) of RV antifreeze in black and grey tanks.

the tank may not freeze but I,d bet the lines will. and the traps.

The part of the tank in the floor will be the empty part as you use water. Never know about MI during Deer Season as some time snow and cold and sometimes in the high 40's. I think I would winterize and use 5 gallon water jugs to be safe. Mallards were never built for more than summer vacation type use. Randu

Will your furnace be running 24/7 while the temp is in the mid teens?
Also 80% exposed with only a heat duct running nearby. Doesn't sound good to me.

There are tank heater pads that you can attach to your tank, but I believe they require AC power.