> The point is preventing another North Korea style nuclear blackmail state
The US and Israel are currently nuclear blackmail states. The rational move for Iran to prevent itself from being bullied is to have nukes like North Korea.
> In this situation it is a fair request by the US
Fair if you're the US, sure.
Especially not when they’re mass murdering protestors and funding islamic extremism left and right
What recent months show us, is that it's a rough world - there are no friends. I'm rooting for European countries to accelerate their nuclear weapons programs. In an ideal world, of course I would be against. But the world is far from ideal. The current alternative is being dictated the rules by Donald Trump or Vladimir Putin. Thanks, but no.
North Korea invaded South Korea, stole a US Navy ship (the Pueblo, which they still proudly exhibit), dug large infiltration tunnels under the DMZ, kidnapped hundreds, or even thousands people from SK (and Japan, to a lesser extent), and have assassinated, or attempted to assassinate, multiple SK heads of state, and perpetrated acts of terror like: https://en.wikipedia.org/wiki/Korean_Air_Flight_858
What did the US or SK do to them before their nuclear program that constituted "bullying?"
Neither of these states have at any point said anything on the modern era that can be implied to be a threat to nuke anybody.
Part of that is because it would be a bad strategy for them, but nonetheless "nuclear blackmail state" and "nuclear state" is not the same thing.
The NPT did not exist at the time of the US developing nuclear weapons, and it explicitly allows US (and other pre-existing nuclear powers') weapons.
Israel, like India and Pakistan, simply never signed it, forgoing the international nuclear technology market as a consequence but also avoiding a treaty obligation not to develop them.
The NPT has much stricter terms for withdrawal, which in any case Iran has not followed.
(The better and much more relevant analogy would be the JCPOA. That's what happens when the US does foreign policy by "executive agreement" instead of treaty. Foreign countries should not value them more than the paper they're written on.)
Perhaps you will argue that the US or Israel or Pakistan or North Korea have conducted themselves in a way where they do not have that moral right either, but that is a different debate, and either way it is moot because they do have them.
Iran signed Nuclear Non-Proliferation Treaty
No. If they wanted self-defense and sovereignty they should have become stronger not weaker after the revolution.