Isn't almost all of Iran's income from oil?
No - its from control of the stock market

Isn't it in their best interest to promote demand for oil?
Probably

Is the threat that they will blow themselves up and diminish the oil
supply?

Now you're just daydreaming. That would be the best thing for us. Even
a nuke would leave the place free and clear in 10 years

Did oil dollars pay for their atomic development program?
Probably not considering how much of the stock market that region
controls.