Thanks! This gets stranger.
Originally I was using a MicroSD Adapter to read the card on a built-in SD card reader in an HP Elitebook 2540P I5 laptop running Windows 10. Today, I used a different micro SD card reader (a USB version this time "T-flash USB") - didn't even know I had one, but found it by chance when I was going through my USB drives in order to install gpartLIVE as bootable drive) on the same laptop. When I looked at the micro SD card using this USB reader, disk manager showed the 256MB partition, another space of several gigs, and a large unallocated space (albeit TOO large). I wiped out the partitions (using Diskpart I believe). Then I saw a capacity of 2TB of unallocated space (on a 128GB card!!!). I got gpart to run on my other Retropie SD Card (never actually needed the USB drive) and using the same USB reader, it too reported 2TB for total capacity. Other Linux utilites reported the same capacity. I tried a different SD card in this USB reader and that reader always shows SIZE 2TB, but it does show the correct partition sizes. Now I had the opposite issue - too much space reported. Various partitioning and formating utilities choked b/c I think they were trying to read/write beyond the actual capacity of the drive. On a whim, I put the card back in the original Micro SD card adapter and disk manager showed 116GB unallocated. I created a simple volume and it worked. I imaged the card and the Pi booted. Almost 24 hours later and I'm almost back to where I started. I thought these adapters were just devices which passed the connection through pin for pin with no 'smarts' in-between. Maybe the built-in card reader had an issue? Dunno. In any case, thanks for all of your help.