My fear is that we blew the "pre-emptive" card with Iraq. Intelligence may have overestimated the probability of a counter-revolution against the Iranian clerics, placing them at a lower priority than Saddam Hussein.
I think it will be extremely difficult to play the pre-emptive card with Iran. Israel has a better hand to play than we do, given their direct vulnerability to the Iranian medium-range missile. As insane as it sounds, world support of the United States would probably vanish (these are indeed times of insanity) if we launched another pre-emptive war on Iran. As long as the Israeli trump card exists, I wouldn't expect the U.S. to strike Iran UNLESS - unless - a terrorist attack occurs on U.S. soil which can be pinned on Iran, or Iran's support of Al Qaeda. At that point, all bets are off.
I think you're right on all counts.
The simple fact that Iran has threatened our troops in theatre with a preemptive attack should be enough to vindicate any decision to take out their C&C. I still can't determine exactly why they're fishing for us to attack them.