AMPLibraryAgent hogging 100% of CPU

I have a gigantic (5TB) music library I maintain on an external drive. I had a brief power interruption to the drive, so Apple prompted me to identify the location of the music library. Because I was in the middle of something and distracted, I clicked the music library file they proposed, which to my horror was the default library xml file that Apple Music keeps on the hard drive. As that library contains only a few albums I once downloaded from the apple store, it overwrite my actual library, and I lost virtually my entire library. 9 days of continual labor and maybe 30 hours of phone time with apple techs later, and I am still in the process of trying to reconstruct a 6 month old version of my library. I'll spare you all the details of that, although one highlight was when Apple broke all the links in my library by arbitrarily inserting a U2 album and pushing my entire library down one level into a second MUSIC subfolder.

The repairing process couldn't begin until AppleMusic went one by one through half a million songs and added an exclamation mark to show that the link to the physical media had been broken. That process of adding exclamation marks took about 35 hours. The next process, which was to get AppleMusic to attempt to restore the links using the indicated location, took over 70 hours.

Throughout this week Apple has bogged down my computer to a ridiculous degree, and I was looking forward to being able to begin doing all the work I've been putting off this week while my computer was basically paralyzed. Unfortunately I seem to still be trapped in an uninterruptable AppleMusic process.

The latest process involves the AMPLibraryAgent using 100% of my CPU while Apple Music states it is "Determining Gapless Playback Information" for a portion of my music library. This portion involves 178,500 tracks. It began performing this process at 10:00 am today. As of 2:00 pm today it has completed this process on only 158 files. If it were to radically increase in speed and complete 1 track per minute, we are talking about my computer being paralyzed for 178,500 minutes, which is an incredible 124 days, or just over 4 months.

This is simply ridiculous. Does anyone have any advice? Can I interrupt this process? The dozen apple techs who have brought me to this place seem to be baffled by the simple phenomenon of having media that I didn't buy from the apple store, or storing media on an external drive. What will happen if I quit Apple Music during this process? What if my computer crashes or forces an update?

Managing these sorts of crises were much more manageable on iTunes, pre-Catalina. Now, in the post-Catalina environment, every single detail of maintaining my music library has become RIDICULOUSLY LABORIOUS. Apple needs to be much less uptight about trying to endlessly shove streaming/cloud services in our faces, and let us use our own music the way we want to use it without these kinds of baffling, labyrinthine, counter-intuitive, labor-intensive processes. Simple tasks , like importing a single album from my own media, takes about ten times as long as it did pre-Catalina; making simple edits to things like name of artist or album title has become really buggy and difficult.