“NOOB” questions about how TC electronics work?

I will leave that to the Ford owners to answer, I do not know how you are wired.

For me, it is very basic, run the fridge on propane. I will add, the fridge is more efficient on propane than 120-volts or 12-volts. But to be fair, if the fridge is cool, you can easily go 10 hours with the fridge off. In theory, the truck has the ability to run the fridge. The catch is, one oops, and you can kill the truck battery. Been there and done that, learned it is not necessary.