Maybe the easiest most efficient least troublesome way, would be to duplicate the setup that is in the other dreamer tt
Same or similar fridge Combo inverter-Charger batteries wiring
Make a list, take pictures of everything, try to obtain all the same components, possible it might cost more than hand picking the items needed, the number and type of batteries is a major factor in correct operation of inverter and fridge, one battery is Not going to cut it! For a residential fridge Install, unless you always use campgrounds with shore power hookup, and the fridge power Via inverter is ONLY during transit, then one battery might work, since the TOW vehicle can supply some bit of power to the tt battery while in motion