nice job sticking with it. If you're like me, the little neighbours kids learnt some new words ......
short story, might help with your morale .... my 95 had a code 82,no check engine light, just sets, google it, bet the only results are mine, anyways, gave up, figured i'm no expert, posted here, nothing, so took to "the best trans shop around here", a week later, "ya, we don't know what's wrong, gave me info on a place that supposedly specialized in old stuff",
and charged me $350.
that motived me to fix the damn thing , it's not rocket science, if you have the manuals and it's OEM, who ever writes them does a get job, thou they over simplify it, haha.
1st and 3rd is weird, is that symtom in the 4L60E_80E_CODE_BOOK.pdf?
and yes it did "fix it" .. new ECU.