I might have made "some" progress.
Late last evening, I was able to create a Linux imaging boot disk on another computer and use it to image all three partitions on my problem machine. The image completed without errors but seemed to take several hours longer than usual. Although this worries me a bit

, I'll have to do a verify and also see if I can mount (and read) data on the created image. If all is OK, I'll have my needed safety net in case my hacking does permanent damage while fixing the damaged Windows installation. I would lose my old snapshots, but at least I should have access to a workable, bootable configuration. If I thoroughly trash things, I can restore the workable image and try again until I get the Windows problems fixed. If successful, I can then reinstall Rollback and (finally) be back to normal (once I re-image the entire drive for permanent safety.)
I'll keep the forum advised as to progress in case anyone else ever runs into a similar situation.