And as far as I know the truck system is isolated from the TC system and does not charge the TC batteries.
There is a wire from the 7 pin connector that goes to the battery on the truck. That power is used by tailers and TCs' to charge the battery in the camper. Ford is the only one that I know that has an isolator that disconnects the power to the 7 pin connector when the engine is off.
Some campers have an isolator built in - which can fail. Test it. Mine does not. When I got my Dodge, I installed a relay inside the camper. (I bought the truck new and I did not want to get the "you modified the wiring on the truck - your entire warranty is void") As I have my running lights set to come on anytime I start the truck, I connected the lead going to the running lights on the camper to the coil of the relay. Then cut the power lead from the umbilical and connected that to the Normally Open contacts on the relay. Start the truck - lights go on - relay closes - I have power going to the camper to charge the batteries while going down the road. Turn off the truck - lights go off - no draining the truck battery.
This happens with the TC just sitting there unused, no lights, no battery draw of any kind.
The propane detector draws power. I discovered the AM/FM radio in my camper was drawing 1/2 amp WHEN TURNED OFF. There are lots of parasitic devices that are turned on all the time in your TC.
The TC batteries and solar panel should be more than enough to run the fridge with power to spare for that length of time.
I would check how much power that solar panel is putting out - and how much power the fridge (and other things) are drawing. What size solar panel? What is the condition of the batteries in the camper? Disconnect the camper from the truck, get out the ammeter and start testing!
-On Edit-
I see you said you have a NovaCool. Those are a 12volt compressor fridge. Not bashing that fridge, (as I want one myself), but you need probably at least 200W of solar and large enough batteries to run that.