Alright, I am struggling a bit - Dave I like your inverter to inverter design but the Cooler/Fridge that I have (CFX-65DZ) specifically calls out not connecting it to a "rapid battery" charger under penalty of death (or at least a broken fridge).
I am trying to think of ways around this and have a question out to the manufacturer since it has its own prioritization circuit for 110V rather than 12V I am thinking as long as it is always plugged into the inverter that the charger is plugged into whenever the van is on it should be isolated. I plan on mimicking your setup - with the plan to add solar at a later date and possibly slightly different battery connection. Really my power users will be the fridge, MaxxAir fan, charging for a laptop, camera, phone, drone, etc., and maybe the occasional electric kettle. The only other solution I can think of would be a 12v socket attached to a relay that pulls power from the van when the key is in the "start" or "running" position and from the house battery when the key is in the "off" position. Thoughts or input from anyone would be welcomed - just trying to figure out the best option before I spend a pile of money and end up cursing myself.