Well, good news at last!
Before wiping the SSD I thought I would give First Aid one last chance in Recovery mode. This time, I started from the disk device level, working down to the Data volume, not skipping any level in between. The Volumes (group) took a minute or so, appearing to unmount the lower level volumes, before scanning the data. Surprisingly, it passed. I then proceeded to the HD, then the Data volume, each also taking a minute or so to unmount some volume before printing anything into the window. Finally, the Data volume was finished and it passed.
I repeated the test two more times for the HD and Data volumes and they all passed.
I'm not certain what I did differently this time. I think in the previous times, I did the Container, then HD, then HD Data and missed the Volumes group. So the Volumes group may be key to fixing this. Or, maybe I'm just lucky this time. Who knows.
In hindsight, I think if I followed Apple's suggestion and did an fsck at the disk device level, not having to worried about Container, group or Volumes, or the order in which it is done, it may have fixed the corruption as well.
Now I'm back in the Normal back, I repeated First Aid on the Data volume (not bothering with group) and it still passed. Here's the output of First Aid on the Data volume.
Running First Aid on āMacintosh HD - Dataā (disk3s1)
Verifying the startup volume will cause this computer to stop responding.
Verifying file system.
Volume could not be unmounted.
Using live mode.
Performing fsck_apfs -n -l -x /dev/rdisk3s1
Checking the container superblock.
Checking the checkpoint with transaction ID 5847775.
warning: container has been mounted by APFS version 2142.140.9, which is newer than 1934.141.2.701.1
warning: disabling overallocation repairs by default; use -o to override
Checking the EFI jumpstart record.
Checking the space manager.
Checking the space manager free queue trees.
Checking the object map.
Checking the encryption key structures.
Checking volume /dev/rdisk3s1.
Checking the APFS volume superblock.
The volume Macintosh HD - Data was formatted by hfs_convert (1933.61.1) and last modified by apfs_kext (1934.141.2.701.1).
Checking the object map.
Checking the snapshot metadata tree.
Checking the snapshot metadata.
Checking the document ID tree.
Checking the fsroot tree.
Checking the extent ref tree.
Verifying volume object map space.
Verifying allocated space.
The volume /dev/rdisk3s1 appears to be OK.
File system check exit code is 0.
Restoring the original state found as mounted.
Operation successful.
So thank you @HWTech and BDAqua for all your help. I think the SSD is fixed.
My next project is to upgrade to Ventura as I now know Monterey is obsolete. From I know from searching around, I just have to go the Apple Store and get the Install macOS Ventura, run it and follow the instructions. That will do the upgrade and I don't have to do any Restore from the backup. Is that right?
Thanks again.