I think an RV refrigerator can take up to 400 watts to run. It's going to run off of the RV batteries, shore power or propane. When running on RV batteries (towing) those will need to be recharged somehow. I don't think the 7 pin DC output can keep up with that load. We had solar panels so there was additional charging capability. I never noticed a low RV battery after rolling for 5 hours with the fridge running on battery but I've heard it can happen. So the RV battery is the critical component here when one uses the RV appliances without AC hook up or propane.
I like Whomever's calculation. I think 240 watts is about max. from the 7 pin.