Japan was at a point when kamikaze attacks didn't do shit to the navy sitting on their shores. Time had been bought, oil was nonexistent.

Again, this is absolutely true but only really knowable ad hoc. If you have a source stating the conditions of Japan were known at this point, it would change my perspective.

The horrors of the firebombing of Tokyo dont make the nukes justified.

Correct, but for the US it's likely to be one or the another. Even in a theoretical blockade, the amount of people who starve would probably outweigh the bomb. There are no good options in war, use of the first atom bomb was probably the one with the least casualties.

You can cease bombings during negotiations.

You can but you're allowing the enemy to re-group. We shouldn't trust the genocidal Japanese government to act in good faith just like we shouldn't trust the Nazis. Every day still at war meant Japan was still slaughtering people in camps.

"There is no alternative but immediate unconditional surrender if we are to prevent Russia's participation in the war."

Which does not say "We must surrender immediately." It says, "If we don't, we'll have to fight Russia as well." One ambassador saying that surrender is a good option is not the Government of Japan saying so.