Thanks for the response.
I figured out the issues. I had to completely empty out banned ips, censored words, etc. to avoid the preferences issue.
Ultimately in order to get my live site updated I had to take the site offline for most of the day (which was not what I wanted to do) download the entire database, run the update locally (to avoid timing out issues), and upload the updated database. (The database has over 100,000 entries, 3,000,000 comments, and 1,400,000 forum comments. )
I am glad the ordeal is over. Conservatively, I spent approximately 100 hours testing and finding solutions to problems (including an aborted attempt back in April). Anyway, it’s done.
I’m currently finding and fixing other issues that have cropped up. I do have a couple of questions: 1) Why no script to update modified member profile templates? 2) Why no mention about the templates at all in the update docs?