3-days is a pretty short time for such a major shift in politics for starters. Would a 3rd or 4th have been justified in the 6 day gap before their August 15th surrender announcement if the US had had them available?

Also the justification for the second bomb, that it was required to demonstrate it wasn't a one off doesn't require the that bomb be dropped on a second city either. The main thrust isn't that the bombs weren't effective it's that the extreme nature of the act requires extreme justification bordering on it being the only option but for a bloody home island invasion. See my other long posts about the anti-moral-bomb argument in this thread, I don't want to duplicate them here to avoid spamming the thread.

Communications between Hiroshima and Tokyo had totally broken down. When input was received on what actually happened, it would have been so fantastic that it would have been hard to process. And this was at a time where the Bolsheviks-hard to understate the Imperial Japanese government's loathing and horror of Communism despite the pragmatic and often deeply mutually cynical relationship they had during the war-were about to go to war with them.