Whether or not Israel could be destroyed with a single nuclear weapon is irrelevant. This is because Iran would be utterly destroyed by the US if it waged a nuclear attack on Israel. Israel is the human with the big foot in my scenario, with the US nuclear arsenal being the big foot.

Iran does not advocate, and has never advocated killing the Palestinians. They have never advocated killing the Jews in Israel either. Iran has no interest in killing Jews. If they did, they would have started with the Jewish population of their own country.