You believe too much. Usually one who believes too much does not know as much. Knowledge does not come from believing but from learning. No, I am not talking about salvation from sin but from universal catastrophes of the size of the flood. I did not say from another flood. It could be fire or atomic destruction. Jesus had nothing to do with personal salvation. He rather said to listen to "Moses" aka the Law to achieve salvation. (Luke 16:29-31) And for him to pay for the sins of others, he would contradict the Prophets of the Most High who say that no one can die for the sins of another. (Ezekiel 18:4,20)
The promise not to flood the earth again does not have to be only with water. It could be with fire or total atomic fall-outs. Jesus will never return from the grave. He was a Jew and he believed in Psalms 49:12,20. The eternal home of the dead is called Sheol aka the grave. Your assumption that there is no difference between the collective concept and the individual one is based on the power of Christian preconceived notions.