You're right, Suki. Since the time that the movie of The Hustler came out, it's success attracted many guys to claim that Tevis was really writing about them. But Tevis wasn't writing about any of them. His book was written in '58/'59 while he lived in Kentucky. The book bears almost no resemblance to the movie's screenplay.
Rudolph Wanderone parlayed a lie into a pretty good score for the rest of his life. But the M. Fats character in the book was nothing like the Gleason character in the movie. Even in the movie, the Fats character was a gentleman high stakes pool gambler who was under the thumb of a mob guy; not a bit like Wanderone, who was a talented ninja-hustling blow hard.
Your point about RA being too young and too distant to have influenced Tevis is accurate. Ironically Tevis was born in San Francisco in 1928, but moved to Kentucky 11 years later, where he lived until moving to my birth town, Athens, Ohio, where he taught creative writing at Ohio University. It is possible that he witnessed Eddie Taylor prior to 1959, but he always maintained that his characters were simply figments of his imagination, and I believe him.
However the screenplay was "adapted" and written by Robert Rossen and Sydney Carroll. Rossen was a New Yorker who was an avid pool player that some described as a hustler. He most certainly knew all the players of the day, including Mosconi. It was his and Carroll's influence that made the movie into what it was. So if any of the movie's characters were even remotely modeled off real people, it was Rossen's doing-- not Tevis's.
Doc