Moved my site from primary domain to a parked domain; broken theme

I did review this, unfortunately, my case was not covered.

https://codex.www.ads-software.com/Moving_WordPress

I have had my hosted domain changed, so that my wordpress domain was no longer the primary domain, but a parked domain. The server was not changing, nor was the provider. My database was also not moving. From the examples in the codex, it looked like it would be a relatively easy change, although the hardest part, changing folders, is not something I could test, since I do not have access to flip the primary domain back and forth.

So I prepped as much as I could. I moved everything into the subdirectory that the parked domain would reference, updated references, and submitted my domain change ticket.

I had to resort to using “If You Forget to Change the Locations” and set up the locations after the admins made the move. This made it so I could log in, but my theme was blown away.

There’s been mention of using better find and replace, but I’ve already made the replacements that I know are safe (e.g. “https://www.olddomain.com” to “https://newdomain.com/olddomain.com”) although there are still plenty of “olddomain.com” references, I am not near enough familiar with my database, much less SQL structures, to know how to differentiate bad “olddomain.com” references from mission critical “olddomain.com” references (for two major reasons: olddomain.com is the subfolder for the parked domain my wordpress is installed to and referenced by my host configuration, and, obviously, olddomain.com is included in many places both for a folder and for references to the parked domain front facing addresses)

After disabling all plugins, and switching my theme to Twenty Fifteen, it’s still all kinds of broken, and most notably, unchanged from before. It looked like this before disabling everything and changing themes, and still looks like this after: https://i.imgur.com/hV3LH3J.png (from https://www.pulppoetry.com/ as of Sept 18, 2015)

If I go into the theme customize section, I get the left side menu, but the preview is an endless cycle of “session expired” login. This is also true when trying to live preview any theme.
Screen shot: https://i.imgur.com/NqT6bj7.png

I’ve seen some advice for “uninstall and reinstall” for similar sounding move problems (although no one seems to have reported a domain shift like this). Except when searching for the “uninstall” instructions for the first half of the advice, I find none and just see advice saying “don’t panic and uninstall!”

So, I’ve been sitting on this for months, not panicking. What else can I try that’s not an uninstall panic to fix it?

If uninstall is the answer, how do uninstall without starting over?