Could Hirohito (Suzuki, etc.) have been convinced by bombs dropped elsewhere?
(our physicists were able to back-of-the-envelope; should their physicists have needed hundreds of thousands of civilian deaths to calculate what an A-bomb could do?)
So I think it's not obvious (multiple books have been written on the subject) what could or should have been done or not done back then; now, from my point of view, those cards have been dealt, for good or for ill.
Personally, I think it was tragic, but there was not much choice. Forcing Japan to its knees by conventional means would have been a prolonged bloodbath (with the Soviets getting in the game as well), with probably a higher death toll.
Not likely, Tokyo was firebombed to ashes and it didn't move him to surrender.
The Soviets had people inside the Manhattan Project / Los Alamos. As the US made progress that information was fed to the Soviets/Russians.