How do we know they do not have nukes? They could buy them from North Korea or Pakistan. They have been assisted by A. Q. Khan, the father of the Pakistan nuke program so we don’t really know if they have nukes of their own design yet.
I have no doubt they would use a nuke, if they actually had one. Those kind of people don’t have the same kind of sense of self preservation most of the world does. Even though the mullahs in control aren’t suicidal themselves, one of them will get old and terminal, and decide to take as many of his enemies with him as he can. I’ve wondered the same about Kim Jong. Can never know what goes on in their head.