Okay, the Coverdisks archive in the Zone has been updated to include an image of the Pinball Fantasies 2 disk. Your Party Land and Speed Devils highscores are preserved!
These non-DOS disks are not nearly so difficult as I had thought. There's a lot of blank space on them.
The highscores table takes up very little of track 1 and was undamaged. I managed to fix the other checksum error on track 63 by importing a block from a Pinball Fantasies 2 disk I own and confirming the validity of the data by comparison with a disk image I had downloaded from the internet.
The other two disks are more extensively damaged, but now I am hopeful that I can get them fixed too within the next couple of days.