“D. Truman inherited a nearly-completed nuclear program in April 1945 - he didn’t push anything. He didn’t even know about the Manhattan Project until April ‘45.”
There are documents showing evidence that Truman he wanted a successful test prior to Potsdam. This is evidence contrary to your statement.
“If they had developed the nukes in one or two years, instead of three, Germany would have gotten it right in the neck.”
This is speculation. There are good reasons both from a strategic standpoint not to drop an atomic bomb on Germany. How are you going to hit something like Cologne where you’ll contaminate French, Dutch and Belgian water supplies, industry and people? You will kill allied civilians.
Two - conventional weaponry was, by far, the better way to defeat Germany.
Three, you say he inherited an ‘almost finished program’. This is not so. They hadn’t even tested the design of Little Boy before they dropped it. They had a ton of theory, but no actual testing to show that the bomb would actually work. Then they used both of the prototypes that they did have in the hopes to force a political solution to the war.
That’s not a very systematic way to go about and do it, is it?
FDR croaked on April 14, 1945, Truman was finally briefed about the Manhattan Project on April 24, 1945 and Postdam was in July 1945; so your "evidence" is crap. They did not magically develop nukes between April 1945 and July 1945.
You say I'm speculating about our willingness to nuke Germany, but it is a fact the the U.S. had over 100,000 people involved in various ways with the Manhattan project, we spent several years developing the bombs and spent 100's of millions of dollars - we were deadly serious. We didn't do all that as a theoretical exercise. You think we risked the lives of 100's of thousands of American troops to an invasion of Europe, but we wouldn't have ended the war with a single bomb if it had been available in time?
"Three, you say he inherited an ‘almost finished program’. This is not so. They hadn’t even tested the design of Little Boy before they dropped it. "
The biggest effort with the Manhattan Project went towards getting fissionable materials for the bombs - uranium 235 and plutonium. Without those materials you don't have a bomb, so until that infrastructure was in place to supply those materials, they couldn't test anything.