Nice job on showing us your install...this is appreciated. On the dual battery - I installed a dual battery system in my 2018 Raptor. I was able to fit the isolator (Hell Roaring brand - solid state unit out of Polson, Montana) in the space on the pass side firewall above the fuse box. I used nutserts at three of the four corners...couldn't fit one in the upper left. I zip tied a circuit breaker to one of the vertical wire bundles that you show in the engine bay pic. This has worked well for me...and I drive on poor roads daily for six months a year. If you can fit your isolator there, it'll be out of the way and pretty much clear of any splashes. I have another of these in my 93 F250 - been working really well for years now. I originally put the fridge and battery in the back seat, tired of that and now have them installed in the bed using Mac's tracks, ARB fridge slider, and aluminum angle to make a battery bracket. I went to an ARB Elements fridge when I put it in the back. I'll send some pictures when I get back to my Raptor at the end of the week.