RE: Running the 'fridge
I'm not to sure what you are trying to accomplish.  Try putting this into
the equation.
First, you can run the refrigerator on propane anytime, stopped or driving,
even though some don't like the idea of driving with the propane lit.
Second, if you have shore power (120v AC) then you just switch the
refrigerator to 120 and forget it, the power is coming from outside the van.
And the 12v cooling is best used ONLY when driving and the alternator is
providing the needed power.  Using 12v cooling when parked and the engine is
off will pull your battery flat in a very short time.
So there would be no need for a converter (120v to 12v DC).