FINALLY got to put some fluid in the old girl and drive her around the block. I'm at least a quart if not 2 or 3 low, but the shift points are pretty much exactly where I expect them to be with the TV cable more or less right where it appears others are and based on the "just before tension" adjustment. It downshifts when I slow down & take turns, and also will easily kickdown just like it used to 11 pages ago.
I don't know that I'll be able to drive it enough today to validate the operating temperature, especially given that I'm a decent bit low on fluid. But I've been thinking through it and if the engine it making it spin faster than it thinks it should be spinning then it's likely not enough fluid is being sent to the places that need it and could make it run hot. Total conjecture, but low pressure is listed as a cause of high temps.
I'll probably only have one or two more progress posts in this thread, if I may be so bold as to count some chickens before they have begun the hatching process. But I want to say thanks to everyone who participated in the adventure, either to troubleshoot, or encourage my nonsense, or just to silently read along. I would love to know that I helped one person save $2k by rebuilding their transmission themselves, but it's plenty just to know that I saved myself $2k. And I learned a whole mess about automatic transmissions along the way.
Special thanks to
@U8MYDZT who paved the way, and (seemingly) didn't get tired of 5 pages of DM's that y'all didn't even get to read on top of these 11 pages.