"The above is pure speculation on my part."
Your theory is perfectly plausible, and fits ALL the facts as well as anything. It also could explain the Moussoui/e-mail angle, maybe he actually was trying to help Moussoui out, and was fully aware of his role as a subversive, if not of his intended terrorism.
There's something a little pat in the way the dad says:My son was a Bush/War supporter. If you were the dad, wouldn't you add something like: even though I told him he was crazy/wrong.?
And there is a complete precedent for this in the Pearl murder. I'm not saying Pearl was a terrorist sympathizer, but he certainly was only after "the story", I don't think he was some CIA op. I'm not saying Berg was a terrorist sympathizer either, he may well have been another mis-guided "peace" activist. I'm fairly well convinced that he had no legitimate business interests in Iraq. I heard that those Halliburton truck drivers are making $8,000- a month, TAX FREE! That shows you just how dangerous it really is over there. Not the type of place to just go dropping off your business cards with potential customers.
Prometheus was a leftist organization, paid for by others "upstream" in the radical hierarchy.