My thanks to everyone for their offers of help, websites, and generally sympathetic responses!! Here's what I've decided to do:
The local camera store has a Manufacturer's recovery utility that I hope will work. If successful, I'll gladly pay them the $25, If not - then I'm just SOL. They seem to think, however, that the card showing continued 'limited capacity' is a good thing, and they feel it may have to do with corrupted directories, which they should be able to fix.

I'll follow up with the answers. Wish me luck.

Best, Dave