Thank you very much knc1! I should have gone straight there after nothing else worked, but I got the update working. And yes twobob, I got the patch from one of those "Stop Big-Brother Mode" posts years ago.
Just in case anybody has the same problem, the debricking sticky pointed to
this thread to debrick. However, instead of going through the whole flashing process (I'm in linux, without access to a 32 bit Windows computer), I just found the file I had patched (/usr/bin/showlog) in the downloadable firmware image in
pastebin (3.0.2 factory image). I'll leave it up to you to get files out of the .img, but it worked for me.