You are right (did Wilson get his info on the documents from the news), that is clear, although the time from the first descriptive news article is only days after the March 3 announcement by the UN; and the IAEA had to do their work looking at the documents before that. But, Wilson COULD HAVE learned about the "forged" nature of the documents from the news.
Yet, as my new addition points out, the factors that make those documents forgeries could have easily and readily been detected by Valerie Plame's division at the CIA, yet from October 9, 2002 to March 3, 2003 the record is silent; there is no screeming memo from her division, up to Tenet, saying "these documents are forgeries"; at least none that her division or Tenet were willing to divulge to the congressional investigators on the joint intelligence committee.
I do not think that that failure was due to incompetence, and therefore I am of the assumption that, at least within days of October 9-10, 2002 (if not long before), Valerie Plame knew the "forged" nature of the documents as did others at the CIA. I also assume that her and Joe Wilson talked about those documents, at least from the time after they came into the CIA's possession and before March 3, 2003. Therefore, I think he is not lying when he talks to Kristof, the Washington Post or The New Republic concerning what he knows about what makes the documents "forged", I believe he is speaking from knowledge, not news reports.
I agree with you on all points - but I just wanted to point out that there is no EVIDENCE in the time-line that Wilson "knew" before he could have known. Of course his claims are either evidence of lies or of a much more sinister cover-up. The Senate Select Intelligence Committee decided on the former, but given the political situation at the time I am not surprised.
However, it would be intersting to find out a) when Kristof spoke to Wilson, and b) if Wilson told him some more specifics about the documents.
Quite honestly, to me Wilson appears to be a very sloppy liar, and I would think it less likely hat he picked up the relevant facts from studying/reading news reports rather than from gossip. And who would have been better positioned to give him some gossip than Ms Wilson?