Good points. I wasn't aware that Egypt had WMDs but that would certainly be checkmate. Iranian bunkers would be heavily attrited by multi-kiloton explosions, though.

American direct action would certainly be out of the question at that point, but I'm not totally sure if American aid would be cut off. With ammunition deliveries from the US, I think Israel would be able to fight another Six Day War scenario by virtue of air dominance.

If the link to America is damaged, though, Israel would certainly fold.