1. Who told you that they had intention to make bombs (and why your source is better informed than all US intelligence agencies)?
2. Who told you that they are going exchange their very existence on killing less than one million of Americans?
Do you mean, that the USA, France and England shouldn't have nuclear weapons? I'd rather agree, but it seems quite unrealistic to convince them that they should give up their nukes.
It's their own business, I simply don't care
Even few hundred nukes Iran won't be able to use them for more than "Minimal Deterrence" (same way as it used by North Korea, England or France). It gives only insurance against direct war on yhe country.
Attack on Wash DC would be simple and obvious suicide and they are not suiciders. Their main motivation is self-preservation, and they are smart guys. Thats why they survived and got more allies than America. And, of course, keeping global economy working, would allow improve American ABD system. Smart people don't try to stop progress. They prefer to lead it.