Okay, zip!
Before I got home I was convinced you had it figured out. (Sidebar: yes, the interior lights were inoperative. I never mentioned it before because I put it down to the numerous badly-executed modifications. I'm talking drooping wires, solder blobs in the carpets, drippy polyurethane glue deposits, partially removed projects, etc. Lesson learned - don't withhold *any* symptoms when asking for diagnostic help).
I had already checked all the fuses, but honestly paid more attention to #25 and 26 which seemed more pertinent.
So, I looked at #9 again, looked perfectly fine. I put a multimeter on it and got the continuity "beeep." I also had enough sense to look at the actual resistance number, and it showed a couple ohms resistance. I don't think it ever actually blew. Looks more like a crack where the loop joins the vertical part. Very deceptive.
Anyway, new fuse and all is normal, including the fuel door lock and interior lights. I'm very relieved and grateful for the help.
Then it threw a misfire code which won't clear. Oy.