I ONLY ANSWERED 5 AND 6!!!
5. The US decided to use the atomic bomb because they wanted to end WWII. Remember America was brought into WWII because Japan bombed Pearl Harbor. In a way this was pay back but from a more logical perspective it was to end the war in the Pacific.
6. This question is debatable. (I actually did a debate in my class about this topic not to long ago). I was on the unjustified side because Japan has already been losing the war when it encounter the US. The US took islands in the Pacific. One by one they took them over but they were taken. Japan was in a bad spot and I don’t think it was justified. It was overkill in my opinion.