Need Help with trailer hitch question

Oh, and make sure you never use the 12 volt mode when you are boondocking, unless you are running a generator the whole time (and in that case you should use the AC mode).  12 volt mode will drain your battery in a few hours.

The tow vehicle can supply charging current to the rv if it is wired to do so..that isn't a given.
Even so it is difficult to supply as much as the fridge draws through typically undersized wiring.

So yes the tow vehicle can help with 12V fridge operation while driving but on long enough trips it may be a losing battle.  
IOW if you are using 10 amps but only supplying 8 amps then you have a net loss of 2 amps, so when you arrive somewhere to dry camp you are already starting with partially drained batteries....
If you have hookups then the built in charger will put it back.
In your trip of 90 minutes you'll be fine-  but if doing 1000 mile/16 hour days like I've done it can be an issue!

Personally- I've never hesitated to use the LP system while driving, only issue I've ever had is sometimes the flame blows out.  In the past I've added baffles or automatic reignitors to fix that.
The fridges in the rpod have the reignitor built in.

One tip-  I use a wireless thermometer to keep an eye on fridge temps while driving-  you can pick one up for about $10 at WalMart or other places.
http://www.walmart.com/ip/Accurite-Digital-Wireless-Thermometer/16888916

Oops hour... Rats

   Duck tape may also work, don't worry it will all work out fine some how. Hope you have a safe trip and a good time.

In.....oops