In case anyone is curious how this saga came to a conclusion:
- I took the truck to my trusted mechanic who ended up spending over an hour at the car wash pressure washing the radiator and condenser with "oil eater" soap - he said there was so much ATF in the fins from when the tranny cooler had failed (had to be from one of the hose clamps since the cooler was pressure tested and checked out).
- He called out the 'sucked in' radiator hoses which I'd tried to resolve by installing a new OEM radiator cap. It turns out a previous owner had used stop-leak and clogged up the hose going to the radiator overflow reservoir.
- Thanks to RumHam26 for suggesting to check the PS reservoir since it also uses ATF - sure enough, the level was quite low and I topped it off before mentioning it to the mechanic. He found a small leak coming from the PS return line and fixed it by replacing an 8" section of the hose.
I've named this entire adventure
red fluid nightmares thanks to Toyota using the same color fluid for the tranny, power steering and radiator. Brilliant on their part.
Thanks to everyone for all the tips and suggestions.