I spent most of the day tracking down all the little bugs in my various divs, css styles, and includes, but it looks like things are all good again. What a huge time sink it is to track down all the relative and absolute path breaks!
For now, the updated layout is working and it appears to work regardless of subdirectory or anything else. That’s “a good thing” since I have no desire to go through that mess again. Now I can get back to packing and thinking about putting some new content on this site.