Update on this.. over the last couple weeks I finally got a new AGM battery installed, and tested systems. Water system works perfectly, all lights, inverter, etc works perfectly. Tested propane tank, it all works, and van also includes (super cool) plumbed in propane line under cabinet that can be used for a camp stove outside the side doors.
The fridge fires on propane, but does not appear to get cold. I ran out of time to troubleshoot this, so it may be something simple, but I won’t get to look more until after the New Year. So in the meantime, $1000 off asking for currently not working fridge.