All these ridiculous assertions that have somehow seeped into the public consciousness originated from Slatzer's book. None of them are mentioned by anyone, anywhere, prior to the 1974 publication of The Life and Curious Death of Marilyn Monroe.
She never kept a diary (as she says in her own words in the above video). There is no evidence her phone lines were tapped, as she was freely making phone calls to Washington, DC in the month before she died, and no one other than Robert Slatzer ever heard about this supposed press conference. Not her agent, publicist, lawyer, no one. Marilyn was a woman who was always discreet and private, never said anything catty or vindictive, but yeah, it totally makes sense that in the society of the early 1960's she would jeopardize her entire career to blast her personal life publicly and destroy the President of the United States. Sounds legit.