"An Israel, if it will be loosing an existential war, will go nuclear against his enemies anyway" I honestly don't believe this is the case. Any Israeli nuclear strike would GUARANTEE the physical destruction of the State of Israel. Iran, with its much greater size, would be in a better position to survive a nuclear exchange (which is exactly what the Iranian leadership has already said). This is a sobering thought for any Israeli with his finger on the red button. It is more likely that a militarily defeated Israel would sue for peace on the best terms it could get.
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: Iran: We have 3,000 centrifuges working at enrichment plant