"The most isolated president in history was Bill Clinton."
That's a persuasive list you compiled....may I borrow it to use for listing Clinton as 3rd or 4th?
1) Wilson
The most damning fact is that he had a near fatal stroke which was kept completely hidden from the people and press. His wife and cabinet ran the government for a long period of time.
2) John Kennedy
Now we know he was so desparate to hide his addison's disease that he relied on illegal drug injections just to function. Now we know that his big diversion was committing adultry in the White House with numerous women, including a top mobster's girlfriend. His brother in the position of US Attorney General was the only person he trusted.....and talk about pre-screened crowds, he would come to a city and the civil servants were given the day off to be the crowd with supportive signs.
3) FDR
I waver on him but the evidence we know now demands he be on the list. Remember, Eleanor was known as his eyes & ears, travelling around the country and the world.....now we know that they barely tolerated each other's company....his presidency was smoke and mirrors until WWII started and he was forced to the front.
I can see your point for the three you list. However, those three suffered from some debilitating medical condition. I submit that, discounting such, Bill Clinton is first among the isolated.....unless you count letchery and drug use as debilitating medical conditions.....