It appears that my proclamation of success regarding partial-forum-recovery was a tad premature. After some use, it has become quite apparent that the old database was way too flaky and was causing a ton of issues on the forums. The only option was to wipe the entire database clean and unfortunately, start over from scratch.
So, although it pains me to say it, everyone will have to re-register for the forums. I apologize immensely for this situation, but there was just no way the old database could have been saved.