OK, I’m a dummy, but just in case it happens to anyone else, I’ll provide details on the lessons learned:
Using the link you provided, I was finally able to re-install AO. However, I had to use files located at: C:\Users\Liralen\AppData\Local\Funcom\Anarchy Online (change “Liralen” to whatever your username is) to recover my character ini’s. In this folder, were a couple of folders named with hex numbers, which I assume are from previous AO installations. I first assumed that the latest one would be the latest date modified prior to the new installation, but it was actually one modified a month ago (perhaps because the one dated earlier today was corrupted?)
I got AO updated, copied the contents of the older folder with the hex name into the newest one. The older folder I used had a “Date Modified” that was a month old, but nevertheless, still reflected a change I’d made to my UI a few days ago.
All was well, then I started up Anarchy Online Item Assistant, which I had up-dated today with the Plus 2019 update, and boom! AO crashed, and repeated the issues I’d had before.
Earlier today I had rebooted several times in my efforts to correct the issue, and didn’t activate AO Item Assistant again until I got everything working fine. It took both uninstalling AO Item Assistant AND rebooting before I could get AO to install again. The original AO installation still no longer works.
All is well now, including character ini’s restored, and I really appreciate your help, Melcom. I’ll pay it forward if I hear anyone else having a similar problem, but I will never remember all the steps it took, hence the long detailed “lessons learned”.