No.

I'm going to tackle this point by point.

Historians generally don't determine that someone is a 'bad person' in a general sense. Patton is generally viewed by historians of the war as a brilliant field commander who left lasting impressions on US Army culture and American memory, while noting he had a 'colorful' personality, frequently ran afoul of politics, and was kind of a narcissist. On the whole he's one of the most memorable personalities of the Second World War.

Many historians do note his behavior was often erratic and there are hypotheses that he his long and rough life had resulted in several brain injuries that influenced his behavior. I'm unaware of any historian who wouldn't agree that Patton was often blunt and a bit tactless, and often didn't endear himself to others despite how endearing he's become in American memory.

I'm unaware of any instance of former-SS troopers guarding liberated camps anywhere, let alone by Patton's choice. This seems a misheard or misstated variation of something that did happen.

In the post-War Patton served as Governor of Bavaria. During his time there he drew controversy in the press and in politics as many former Nazi officials retained their posts under his occupation. EDIT: These men were not SS and as far as I remember were civilian officials and functionaries, not party leaders or soldiers.

Patton defended this as saying that many people were compelled to join the Nazi party to have jobs (this was true) and he called the Nazis a political party like Democrats or Republicans and that it shouldn't be the position of the occupying forces to make determinations about German politics (maybe a good moral position in abstract, but very bad PR at the time). This caused a stir for Eisenhower at the time and was the latest in a long history of PR blunders concerning Patton.

It resulted in his governorship ending. Patton died in a car accident on December 8, 1945 still holding his rank but everyone at the time knew his career was effectively over at that time. He was not fired. The Army doesn't fire people, it discharges or simply stops promoting them and lets them quietly retire. He was basically put into an unimportant command while everyone waited for him to retire.

I've heard the story that Patton secretly planned to invade the USSR before, and frankly it's nonsensical. Patton never secretly planned to invade the USSR, least of all with former SS soldiers. Operation Unthinkable was a British war plan and for some reason is often conflated with Patton. Patton had nothing to do with it. EDIT: In point of fact, the Brits didn't like George much.

Patton did advocate a more aggressive stance against the USSR, and this did impact how he was viewed by his peers post-war but Patton was never planning to go cowboy and do it on his lonesome. His vehement position did influence the end of his Army career though, as Eisenhower and many others knew Patton was commonly quoted in the press and they worried his saber rattling would unnerve the Soviets and increase already high tensions.

A lot of this is ultimately tied into the conspiracy theory that Patton was assassinated... by someone... for some reason.

It's an old one, recently returned to popular attention by Bill O'Reilly's garbage book Killing Patton. But it's nonsensical, especially because none of the reasons for why someone would want to do such a thing actually pan out. Patton was one of the oldest men still serving in the Army at that time. Many viewed him as a great leader of men and an excellent commander but no one really ignored the way he could make a stink in front of a camera just by talking.

Patton was a lightning rod for public controversy even before the war. During, slapping incidents had stirred anxiety about his fitness for command. He made frequent gaffes in front of the press, one of the most famous being his calling injured veterans "the real heroes" of the war which was seen as insulting by the families of those who'd died. It's a bit ironic actually, as his quote about fools and dying for their country is one of his most well known quotes. At the time it caused a lot of negative stir for him.

When Patton was reported as speaking out against denazification (and he was) in 1945, that is what ended his career mostly because others had finally grown fed up with playing goalie for the man.