Good stuff here and very accurate for the most part. I knew Walter Tevis and he did say that Fats and Fast Eddie were fictional characters. BUT, he was definitely influenced by the characters and hustlers he encountered in the poolrooms in Lexington, KY and Louisville, one of them being Eddie Taylor. Taylor was an impeccably dressed gentleman who was considered (rightly so) the best pool player of his era (much like Fats in the movie). His biggest challenge was from a young upstart from California called Fast Eddie (Ronnie Allen's nickname in San Francisco).
My feeling is that players like Taylor and stories about Ronnie may have been the inspiration for Tevis to write the book. He did "create" the characters in The Hustler, but every writer needs inspiration from somewhere. Walter definitely saw Taylor play! How much that influenced him only Walter knows. He was a proud man and did not want to share the credit with anyone else, especially not a pool hustler.
Did you know that Fats (Wanderone) sued Tevis and 20th Century Fox in Federal court? It made front page news in the early 60's. Fats lost the case but retained the right to use the name Minnesota Fats. He had legally changed his name, a brilliant idea that made him rich ultimately. No one remembers that he lost the courtroom battle, only that he won the "war."
A few little factoids for your perusal.