I think when dealing with Iran as a first step it is always useful to remember that Persia is one of the oldest cultures in the world, probably had the first large-scale industry (copper mining), and was already a full-blown empire reaching from the Bosphorus to the Indus when in Europe folks had just freshly figured out how to do iron.


On topic: Iran has it easy compared to a Western crusader, especially down on the lower Tigris. Same people, same culture, same religion, cross-border family ties, &c. Easy to be the fish here. And then the Iranian secret service has this strong triade of military, economic and religious power. And also they have a mission, it's not a "job" for them. They operate from a commonly agreed strategic basis, which is: get the Western crusaders. So even sympathetic non-members, or those who want to play it safe because they know they and their family will have to deal with the Persians much longer than with the Westerners. Passive support. Very much like with the Mafia.

The West can't do anything about it, realisticly. But I think the good news is that the Iranian Mafia is forced to keep to their cultural environment and their people, so besides Iranian refugees, expats, agents and a few opportunists in the West the influence will not spread. Btw, those groups are a worthy target of Western secret services.

I think one of the potentially weak points of the Iranian secretive organisation is the need to invest their substantial capital outside Iran. Probably a lot in the Gulf states and the Far East, but via the usual suspects Swiss and Channel Island trusts also in the West.
"Potentially weak" I say because the West is not particulary efficient (or keen) to keep grey and black money out of the system, so the political will for a little covert economical warfare is probably slim.

And regarding your third point: I wouldn't dare to count on any friends and allies in Arabia, regardless who they think should have been successor of the Prophet. Really. We are on their home-turf. And beyond a few suicidal opportunistic Shias I doubt that

And I'm pretty sure Quds is almost completely autonomous short of open war or something stupid like a dirty bomb somewhere (which is not in their interest - they thrive to a good part because of that underclared proxy-war in Iraq). Like the SS was, or the ISI is. I think as long as Iranian officials can handle it like Mission Impossible "Your mission, should you decide to accept it..." they can do pretty much what they want. Their head-honcho is a voodoo master! As if that old fart knew about operational details!