Wow, so much to unravel here.
Yes. The scientific background was in the open. So it would be just a matter of time. And then the point Swansont mentioned:
That is true, more or less. But Japan simply did not capitulate. So the war could have taken much longer, taking many lives of American soldiers.
Yes, but only after Germany was defeated. Heisenberg was in charge. The infamous meeting between Heisenberg and Bohr in 1941, gave the latter the impression that the Nazis were making serious work of the atomic bomb, and brought this impression to the US.
Yep. I have seen the 'atom cellar' in Haigerloch:
Does not quite compare to Los Alamos, is it?
I would not put my hand in the fire for this, but it surely was a reason: Truman said something like this about the Soviets and the atomic bomb: "Now we have a real hammer on those boys". Another reason might have been to have a 'real live test'. A hint for this is the second bomb. One of the A-bombs was a U-235, the other a plutonium bomb. Wouldn't it be interesting to compare their effects 'in the field'?
About the capitulation of Japan: there was a struggle between the civilian government and the military. The government wanted to give up, the military wanted to fight until the bitter end. One of the struggling points was the position of the emperor. The US wanted an unconditional capitulation, the Japanese government found that the position of the emperor could not be discussed. In the end the Japanese government made a very unusual proposal: let the emperor decide. In the meantime the first atomic bomb was dropped. If this fact had an influence on the decision of Hirohito is not known, fact is that he chose to capitulate. His speech in which he called for the capitulation was recorded, to be brought to the Japanese radio studios. Radical militaries tried to steal the recording on its way to the radio station, but they did not succeed. Hirohito's speech was broadcasted, and Japan capitulated. And the US more or less let the emperor untouched. Had the US made it known that the emperor could stay earlier, Japan might also have capitulated earlier. Maybe the A-bombs would not have been necessary.
Main source: Bert Röling, who was a.o. member of the International Military Tribunal for the Far East (also called the Tokyo Tribunal, similar to the Nürnberg Tribunal in Germany).
Hmmm. Lise Meitner and Otto Frisch were hardly Nazis, they were Jewish and fled Germany in 1938. Otto Hahn:
Fritz Strassmann:
So four of the 'main characters' were definitely not Nazis. Equating 'German' and 'Nazi' is simply wrong, also during WWII.