Glad to see you return for an update. I started reading this thread and realized it was OLD but kept reading, somewhere in there, someone asked about The 25 amp vs the 40 amp and I was thinking, "thats part of why he upsized the wiring, so he could upgrade if needed" and sure enough that is what you did.
One other thought is that it might be of benefit to remote mount the fuse for the 12v element that burned the connections, some sort of inline fuse holder, with large enough wires, or a standalone fuse holder wired to the circuit board with heavy wire.
I have a Bigfoot trailer and intend to upgrade the battery system on it to a couple of large AGM's and when I do, I will install a Redarc unit and the cable from the front of the truck to the rear, Circuit breaker up front, Anderson connector, all of that. I do not have a three way fridge, but it seems that it would be a good thing to have, since you are able to make it operate properly on 12v. Somewhere I read of someone having problems with a propane fridge not holding a fire on the road and they install a piece of A/C fiberglass filter on the inside of the side vent to dampen the wind stirring around in the compartment and the unit operated fine after that.
I had been looking at the Redarc units in part due to their environmental sealing that would allow me to mount the unit on the tongue of the trailer under the fiberglass cover.
Thanks for the info.
Charles