Someone better on the Googles than I am found an obit site that didn't require a credit card to access information. So I now have a definitive date of death for Uncle Charlie; September 1st, 1983. It also gives the city and state of last residence, which matches what I found for someone who may be his widow. A letter will go out to her in today's mail; we'll see if she responds. Previous attempts to contact her shortly after Uncle Charlies death were not answered, but maybe time will make a difference. I also did a little name-dropping. Other than his second wife, my father is the only family member Uncle Charlie ever mentions by name in his published writings that I've been able to dig up so far. Maybe that will help.
I also have a series of scans of the one book he self-published, I Search for the Portals. It's straight jpeg files, so I'm going to attempt to transcribe the text and build a webified version here. We'll see how it goes.