I finally got back to genealogy and took another look at your reply. I think you may have misinterpreted the intent of my original query. I wasn't looking for generic suggestions on how to do genealogical research, which I have been doing for over 50 years. Rather, I was hoping that someone out there knew something specific about the people I described that could help me determine possible relationships. Most of what you suggested, I have already done, especially digging through lots and lots of Pennsylvania birth/baptismal records. I did find a couple of births for a child named Frederick Miller, but no information that would allow me to connect them with my ancestor Frederick Miller. I was hoping that the DNA connection to a descendant of the subject George Miler would lead me to the answer. I discussed all of this in the referenced documents.
As for newspapers, they were quite rare in the period of interest, especially in rural, frontier areas like Clark County, Ohio, of the late 1810s/early 1820s. Moreover, even if an obituary were found, the odds of it naming Frederick's parents are pretty close to zero. If his survivors or neighbors, who almost certainly would have supplied the information for an obituary, had known who his parents were, his grandson who published the genealogy of him and his descendants (and who was a college history professor who grew up on the Frederick Miller homeplace) would have included that information. Indeed, he stated in his book that he did not know his grandfather's birthplace or parents.
Put another way, what I'm really hoping for is a George Miller descendant who has unpublished information that might include, or somehow point to, a relationship with "my" Frederick Miller.
Thanks anyway for trying to help.