things to remember
that fridge will be on during the day, drawing power from the the battery and hopefully the truck charge connection
two batteries on the 5ver should carry the fridge overnight
the next day, the truck charge circuit has too recharge the batteries and supply the power for the fridge
whether it can do both, will depend on the truck alternator and tow pkg wiring
many people here 'do this', and some had to upgrade the TV charge wiring,
some did not need too
the question really is, what is the tow vehicle, what is the 5ver
members with the same or similar combo can give you a better answer