You'll be pleased to know that I'm beginning to agree with you on the former point. The more I learn about it, the more it seems that Iran had every reason to be afraid of an invasion by the US. The rest of the world had good reason to fear that the US would attack Iran as well, but of course few considered that catastrophic action a possibility in those early days.
As to the latter statement, it is very true today, but it wasn't always true:
http://www.washingtonpost.com/wp-dyn...700727_pf.html
Iran apparently tried diplomacy, was rejected, and tried to do what it could to avert war with the US. Their decision to keep their halted nuclear program secret may have been fueled by the consideration that the US would not believe them if they said they had shut it down.
At this point, you'd probably be tempted to argue that the threat of war accomplished great things by getting Iran to do so much. It apparently did. However, this does not prove that diplomatic pressure would have been ineffective and it is not what your original point was. Your original point was that Iran would never negotiate or compromise, that it would continue unless the US violently deposed the Iranian government, that it is the mirror of the threat that Iraq was portrayed to be in every way except imminence. The threat of force is not force, and the two should not be equated.
You may also be tempted to argue that the threat of force means nothing if the US doesn't attack countries to prove that the US means business. That's true. It wouldn't mean much if the US didn't go to war with other nations. This has the consequence of encouraging conflicts that could be resolved by threat of force instead, and of course does nothing to demonstrate the futility of diplomatic action.