I'm sure that Saddam's use of chemical agents were thought to be free from "repercussions" as he had Western support at that time, Russia and China were weak and sure enough the West made no move to remove him from power till after 9/11, an event which had absolutely nothing to do with the late Mr Hussein and occurred many years later?

I'm a it confused about your talk of "chemical storage cylinders" versus armed munitions, I am aware that you know much more about these matters than I do, but I suppose sarin COULD be delivered at reasonably close range by using mortars?
So is it not possible that the terrorists had obtained a small stock of gas which was subsequently spread by detonation of conventional high explosive?