Let be clear. Israel won't ever nuke any country. Israel is more advanced and dealing with Iran doesn't need to be stupidly. I think there are things you don't consider. One is Iran is a chance for Israel. It causes Israel be closer to her other enemies. Iran is filled with problems, and it shows how an enemy of Israel will look like. Iran doesn't have military might to be in a real war. Israel has it. But Iran brainwashes not so open country the same way North Korea does it. So that a lot of people go to war.
Thankfully, Israel is very advanced in technology and can use other means. As you know, Iran seeks to copy Jewish made technologies such as nuclear and at the same time Israel tries to be more advanced in air defense like arrow 3 to prevent such attacks on Israel.
Israel should prevent Iran obtain Nukes at any price, but know this: Not necessarily with a nuke attack. Israel can do much better things: It can separate Iran into pieces, and no more an Iran country exist, but some countries. Even in attack there are better options like Nuclear plants in Iran. An attack is an attack, but a genocide is not an option ever.
Israel threatens Iran, because Iran threatens Israel. It is a clear thing here. I don't even support biological wars, which is smarter than what you said above. But there is a fact, Just is a simple plan to do something because you are scary of it, you must know what they can do against Israel, not much real. Israel can occupy Gaza and Lebanon IF THEIR RISK was real, but it is not..