After very much troubleshooting I have managed to undo the inexplicable thing that took down my entire site sometime last night. I suspect it was an automatically updated plugin (in preparation for WP 4.2) that borked things up. Exactly which I have no idea since things just sort of magically started working after cleaning out and reinstalling my theme and plugins. And I’m not one to question things that work even if I don’t understand the why or how of it.
Anyway, no, I am not dead. At least not as yet.