I spent more time than I should have in researching errors and learning how to debug and asking my host to help with configuration changes - even at the cost of other tasks that were time sensitive and actually would have been enjoyable to do. I just couldn't rest until I figured out the problem, and after all that I found out it was a problem with how the theme functions and how it writes option selections to the database. Really glad it was not something I did along the way! So at least I know what it was, I will avoid that theme from now on, and I can rebuild again. And if something like this happens again, I will be able to head it off much sooner and more effectively.
Granted all that troubleshooting was a really good learning experience; now I know all about .ini files and config options and php ticks and cache plugins and page loads and web optimized images and minifying and....but at some point you have to stop trying to fix something that is broken beyond repair. Again, good lesson, but enough is enough ;-)
Now to get done all the tasks I have been putting off because of this ;-) Will return to my MF site once I get caught up on other things. Stay tuned, it's going to be great when it's done!