Kennedy admin officials are the primary source of the "JFK Conspiracy Theory" in that basically the whole administration thought it was a coup... except for apparently McNamara. This is mostly because LBJ acted like it was one, and this includes fist-fights between staffers in the white house.

Believe it or not, I absolutely do believe Oswald (a communist terrorist) shot JFK. It's actually pretty clear to me that that is the case. Sirhan Sirhan shot RFK, but I doubt it was simply him being a lone wolf.

The Secret Service just wasn't what it is now. That being said, I'm not confident the SS would like to see RFK dead. It'd be another huge embarrassment, and from all the leaks of the Obama admin, the SS fucking hate Joe Biden. I distinctly remember one leaked bit of information getting out about how an agent nearly punched him in the face because he groped the agent's wife.