What a long, stupid trip it's been. Data Rescue 4 saved my bacon in a big, big way. I thought I had lost 20,000 songs. In the end, I lost only 215. I can live with that!
Since then I have made two backups of my entire library, and even as we type I am uploading my iTunes library to Google Play Music. Yes, I am uploading all 30,000 files. Backing up my library via hard drive took all night. I can't imagine how long this upload is going to take! Then again, Google said that it'll match all it can from its own library and upload the rest. Still, this is gonna take a while.
I still have a lot of work to do before I can wrap all of this up. There are tons of playlists I need to export, and I can only do that one at a time. Then I'll need to import them to the new library. After that it's all about disk management. Now that I have a new external HD devoted exclusively to Time Machine, I need to move a bunch of stuff around to make room. It'll be worth it in the end. For now, though, it's a slog.