All the Milteer stuff is nicely gathered here:
https://www.maryferrell.org/pages/Predictions_of_Joseph_Milteer.html.
No one denies that Milteer's statements to Somersett were startling, especially the part about picking up a patsy within hours. So were some of JFK's own statements about the possibility of being assassinated. So is the bogus factoid of "Lee H. Oswald's" signature at the Museum of Atomic Energy. The article from McAdams' site that I linked puts some context on Milteer's statements that make them seem somewhat less startling - but they were indeed startling, no doubt about it.
I simply raised two commonsense questions: (1) If someone actually had foreknowledge about an impending assassination of the POTUS, would he be likely to speak freely about it to a character like Somersett, and (2) would he be standing in full view at the scene of the crime? You are free to answer yes, but I tend to think probably not.
Let's apply some additional common sense:
Milteer was a high-profile, right-wing racist. He was a member of the notoriously violent Dixie faction of the KKK. He was active and prominent in the right-wing, racist Congress of Freedom, National States Rights Party and Constitution Party. As a member of the latter's board of directors, he had helped formulate plans "to put an end to the Kennedy, King, Khrushchev dictatorship over our nation.” Somersett described him as "the most violent man I know."
1. If you were planning an assassination of JFK, does Milteer sound like the sort of character you would bring into the loop and trust with your plans? Your kitchen-sink conspiracy theory at the Ed Forum has LBJ, the Secret Service, the Mafia, rogue elements of the CIA, and rogue elements of the military as participants - do you seriously think they'd bring Milteer into the loop?
2. If you think Milteer was actually front-and-center in the assassination planning, doesn't this pretty well lock you into a conspiracy theory quite different from LBJ, the Secret Service, the Mafia, rogue elements of the CIA, and rogue elements of the military?
What I notice about CTers is they never seem to care if their conspiracy nuggets hang together or make any coherent sense. Milteer is just "proof of a conspiracy" in some generic, free-floating way. Try to fit him plausibly into an actual conspiracy theory and you hit a brick wall.
Because there actually were rumors of an attempt on JFK in Miami, my guess is that Milteer may have been plugged into those but that this simply had nothing to do with the JFKA. I always have in the back of my mind Gerry Patrick Hemming's statement, "I know for a fact plans to kill JFK were in the works. Maybe Oswald just beat 'em to it." (A paraphrase - he said something pretty close to that.)