Presuming that he wins in 1952 (Eisenhower stays out):
1.) Ego wouldn't effect policy.
2.) In regards to NATO and the UN, he likely wouldn't have strayed from Eisenhower's policy.
3.) LIkely continues to support Israel as an anti-Soviet bulkward.
4.) In regards to New Deal, he likely continues it. The New Deal and other entitlement programs were popular and he would have to support it to get eleted. To quote Eisenhower
"Should any political party attempt to abolish social security, unemployment insurance, and elimante labour laws, and farm programs you would not hear of that party again in our political history. There is a tiny splinter group of course that blieves that you can do these things. Among them are a few other Texas oil millionaries and an occassional politican or business man from other area. Their number is negligible and they are stupid."
Source
5.) Segregation/Race Relations: Here's an
interview from Thurgood Marshall on his dealings with MacArthur.
MacArthur supressed a black military uprising in the Phillipines in 1942. This may not be so much an example of racism as it is MacArthur putting down a violent mutiny during war.
Apparently he was inspired to military service after his mother told him as a young child that he needed to "grow to be a great man like Robert E. Lee." However, he did have a mix-raced girlfriend in the 1930s when he was in the Phillipines. Furthermore, he didn't hide the relationship and was relatively open about it. See this link for
interview on these two topics.
IMO he seems like a "Law and Order" kind of guy who wouldn't necessarily push for civil rights legislation, but would enforce any pertinent Supreme Court decisions (i.e. Brown vs. Topeka Board of Education)
6.) Korea: He wouldn't use nuclear weapons against the ChiComs or the Norks unless the US was on the brink of defeat. All of this talk of him being a loose cannon with nuclear weapons is a bunch of nonesense.
He likely would have bombed bridges on the Yalu and ChiCom supply depots and military bases in Manchuria. He was committed to forcing the Communists to an armistice along the pre-war borders. he believed that failure to defend Korea and to take a strong stand against the Communists in Asia would invite an all out invasion of Europe.
Link for more information on MacArthur in Korea:
https://en.wikipedia.org/wiki/Douglas_MacArthur#Korean_War
7.) Cold War
writ large: He likely continues America's military buildup and expands deployments to Europe and Asia. he was very pro-NATO and anti-communist, but supported containment and not confrontation with the Soviets and thus likely doesn't depart from the Eisenhower adminstration except for in Suez Crisis and Vietnam.
In the former he likely backs the British-French coalition against Egypt in order to check a Soviet ally. This could lead to a general war with the Soviet should they intervene to assist Egypt. However, such a course of action is unlikely as Khruschev admits in his memoirs that he was "
not seriously thinking of going to war"
In regards to Vietnam, MacArthur is more likely to stage a military intervention to help the French troops at Dien Bien Phu escape their envellopment. See
Operation Vulture for more information
MacArthur didn't run for President as he wanted to ensure that the reconstruction of Japan was completed before he left.