The 7-pin will help while your fridge is on propane, but not do enough while the fridge is on 12v if it is a 3-way fridge.
If the fridge is cold already before leaving it will stay cold that day till you get there if you leave the doors closed.
You need a battery in the TT to tow it (it's the law) so the emergency breakaway will work.
With the required 12v battery and the 7-pin, now you can use the 12v mode on the 3-way fridge and it will help keep it colder than without.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.