Gosh, I'm sorry you had to put in so much time only to feel like you somehow failed. I'll give your suggestions a try. Do you think there's a chance I could read the CDs using a VM running XP and the original Roxio software? I have VMware Workstation on Win 10 and Parallels on an iMac.
(Side story: I had an older CD written with unknown software. Win 10 said the CD was corrupt. Win 8.1 on my laptop showed a UDF reader by Adaptec. Running that didn't help. The iMac showed the full directories, and I was easily able to copy the entire backup to a flash drive. Unfortunately, the iMac was no help with the Roxio backups.)