Why Oswald instead of anyone else. I am a long way from well-read on Oswald but what I have garnered, is he was really an anti-social individual. How would someone like him possibly get information from any high-ranking person? It is hard to imagine someone with his nature being good at securing information. You have read a great deal more on this Russian subject than anyone I know. Does he really seem like a person who would be good at it? Granted this whole Russian defection seems strange but everything about him is strange. but that does not make him a spy, just odd.
Perhaps you should read Newman's 2008 version of
Oswald and the CIA (in which he accuses Angleton of being the mastermind), and his 2022 book,
Uncovering Popov's Mole -- which he dedicates to my hero, Tennent H. Bagley (look him up) -- in which he says he was wrong to accuse Angleton of being the mastermind. But do by all means disregard the parts where he says Sergei Papushin was a true defector, that Oswald was a Ukrainian (sic) KGB agent in Minsk, and that some evil, evil high-level American military officers killed JFK because he refused to nuke Moscow and Peking in 1963, won't you?
(Once a published tinfoil-hat JFKA conspiracy theorist, always a published tinfoil-hat JFKA conspiracy theorist, I guess . . .)