Not taking into account all of the problems with this scenario, including the failed mentions of other Balkan states, French Indochina, and the Raj:
Assuming that the war doesn't escalate into nuclear attacks against the United States, particularly the Mid-Atlantic, Truman would demand access through the Suez and Gibraltar, and neutrality in the Raj, French, Portugese, Belgian, and Spanish Africa, and the recognition and aid of a friendly Soviet successor state. The Axis would demand recognition of territorial gains in Europe, Scotland, Ireland's control over Ulster, the reorganized English state, the established governments in the Middle East, and of both Japan's gains in China and its state led by Puyi, and neutrality in Iran and Scandinavia, and immediate peace at current territorial gains and losses with Japan, and lifting of all embargos, and free and unrestricted trade through the Panama Canal and with South America, and the recognition of any future state which liberates itself from Soviet successors (i.e. the various Central Asian states, Outer Manchuria), and a plebiscite in Commonwealth members and the African holdings formerly held by Axis countries over neutral independence. I highly doubt that this would be accepted, considering Truman's zeal and foolishness, but these would be demands in my cursory opinion. The plebiscites are probably the most unrealistic.
>Fate of Japan?
They'd parade themselves as having won the greater victory, having completed conquest of China at the loss of Pacific holdings. However, eight to ten nuclear attacks would be cause for public outrage unless they can take perception away from that. Germany and France would help rebuild the nation while a Northern campaign for the Siberian coastline under the justifications of peacekeeping and economic security would be waged, though mostly by foreign troops as Japanese troops would be more focused on quelling rioting and reconstruction efforts at home. Whether the outcome is the organization of the previously mentioned friendly Soviet successor as a puppet or a Russian Manchuria is anyone's guess. I'd expect an economic miracle to occur as in real life, but the Americans would be replaced by Germans. While the more zealous would throw a hissing fit over their existence, I doubt that the Japanese would ever see the East Indies or Indochina outside of economic influence by the zaibatsu.
>Decolonization and Industrialization of Africa?
I'm extremely doubtful of the latter and certain of the former. Germany would be far more eager than even the real Soviets to push anti-colonialist messages, especially since the new states wouldn't have to adopt anything similar to Soviet socialism. Industrialization would only work in sparse cases, but Truman's popularity would be in the dumps as peacehawks are vindicated. I don't see anything similar to the Marshall Plan happening in Africa that isn't in name only.
>Legacy of FDR and Truman?
FDR would be seen as more of a patriot than he is in real life, a Lincoln-type figure who died too early. Truman would be divisive, if he wasn't voted out or impeached and agreed to peace, in that he agreed to a loss for the free world but kept the US from waging a war that would be unwinnable for allies that never did much of anything for the United States.