Okinawa was technically Japanese soil, with the civilian population that goes with it.
Those are wildly at variance with the sources I've seen. Max Hastings, despite his tendancy to editorialize, offers 40,000 dead and several hundred thousand wounded as the expected cost of Operation Coronet, which is just invading Kyushu. The Honshu invasion was expected to be worse.
The Joint War Plans Committee gave an estimate of 193,500 casualties on June 15, 1945, including 40,000 dead and 150,000 wounded. The given estimates were for the invasion of Southern Kyushu, followed by the Tokyo plain on Honshu. Those are the official estimates from the time, total, and hindsight matters nothing for the perceived motivations of the bombings. MacArthur endorsed those estimates, based on a number of reasons. One of the most prominent being the high number of potential landing sites. The Japanese military would be unable to position all of their troops at a guaranteed point of assault, and casualties would be much lower, as a result of that, since a large percentage of casualties occur during the breaching assault.
Also, yes, the top commanders were aghast. They don't have the benefit of hindsight. The firebombings had not convinced the Japanese government to surrender; the total blockade caused by aerial mining once the B-29s were pulled off the firebombing mission had not caused them to surrender. They made overtures because of starvation two months before the end, but then withdrew them, signalling they were willing to continue the fight. They were known to be diehards from a myraid of engagements by now. A completely rational enemy would have surrendered after the Marianas, a merely desperate one after Leyte. Japan might be defeated by any rational standards, but they were now far beyond rational behavior.
I will grant you that they were not acting rationally, but do you know why? The Japanese military wanted above all else to preserve the institution of the Emperor. They knew the war was lost, but they hoped that a final, decisively bloody campaign would persuade the US to accept the condition that Emperor be allowed to remain in place during their surrender. Yes, a small minority of die-hards did attempt to prolong the war after the decision was made, but they lost, and are unimportant. However, even that small core of fanatics was motivated by a desire to see the Institution of the Emperor survive, mostly because the Allies had called for nothing less than Unconditional Surrender. In fact, it was almost entirely that small minority that prolonged the war due to its influence in the Japanese government.
I am having trouble finding the reference at the moment, but by the beginning of August, nearly half of the Emperor's advisors advocated accepting the Unconditional Surrender declaration at Potsdam.
And the "single veteran" point was worded more carefully than you think; the people who would have had to do the actual invading, the infantry, tankers, artillery enlisted, NCOs, junior officers? I doubt you can cite a single source where they were against the decision. They also happen to be the only ones you can still meet.
Touche. However, people like that normally are not the voices of history for the books. As such, it would seem difficult to confirm or deny that statement on any level for the time being. Please do not misunderstand that I am against the dropping of the bomb. I firmly believe it was necessary. However, it was not necessary for all the reasons people like to think of.
Interesting fun fact for those not currently arguing: The March 9-10, 1945 firebombing of Tokyo caused more immediate deaths than the Hiroshima explosion, over 83,000.