The fan is just a cheap one from Lowe's or Walmart (something like
this), cost about $15. It does not have a thermostat, just fan, 600W, and 1,500W setting. To control temp, I break the hot side of the power feed with a
baseboard thermostat.
At those temps, not sure you could make two weeks, but you should make about 10 days with a decent unit and twin tanks. Typically, you are limited to about one week of groceries, water, and sewer anyhow due to limited space.
Power consumption is a whole other subject. With about a 200W solar unit or small generator, you could probably do what you want with ease. Without solar on one or two batteries, you could only make a couple days per battery at most. Hopefully someone else will give you a link to some good 12v tutorial that will show you how to calculate what you need. (I looked, but couldn't find the links I was looking to give you).
Another factor is how long you plan on sitting still. I am almost always on the move. Without, I could get two days out of one battery, including one recharge of my laptop. Fortunately, my current truck tops of the battery with only two hours of highway driving or three hours of slow cruising.