2007 Voodoo blue FJ cruiser
hahahaha I’ll be sure to do that before I leave today 😉"Probably"
But you took photos then cleaned it all off, so that you'll be able to tell if there are any new coolant "leaks," right?
These clues say to me to make sure you have checked the transmission, transmission fluid, and transmission cooler well enough... From reading the summary and timeline, it looks like you haven't really dug into those yet. Your transmission cooler isn't gunked up or anything (inside or outside), right?
Automatic Transmission FJs have a portion of the main engine radiator dedicated to cooling the transmission - the little hoses out the bottom of the radiator. If you have an aftermarket transmission cooler, someone had to have disconnected those and... done something. Added your transmission cooler inline? Bypassed the original transmission cooler altogether? You mentioned you had your radiator replaced as part of this. Who did that? I don't suppose you have photos after your transmission cooler install and before the radiator replace just to double-check that the radiator replace didn't change anything out from underneath your assumptions about the transmission cooler?
And as for the transmission cooler, I installed that myself a few years ago. It is attached to the condenser on outside of the radiator, and is inline after the radiator transmission cooler and before the transmission. My transmission temps have not changed at all throughout all of this, it hasn't been getting hot whatsoever. It sits pretty steadily at 140–160F. I’ll give it a solid look over and see if any of the fluid is leaking or if the transmission hoses appear damaged or worn, or routed differently from when I did it. I can’t imagine if my transmission temps were so hot they overheat the engine but showed as normal on my gauge. But I’m not opposed to looking at anything. I’ll look it all over this evening and report back.