Unfortunately this post falls into a lot of the traps that conspiracy theorists, both from the left and right, often engage in. Your second sentence, which I bolded, is the only piece of purported actual information in your entire post, and I'd be interested in seeing the source for it. I must tell you that I don't trust Seymour Hersh, nor do I trust Egyptian intelligence. I would agree with your assertion that if 2013 turned out to be false, that would make this latest use of chemical weapons more questionable. But, and no offense, your evidence for this seems very flimsy to me, and you provide NO evidence for the doubting the most recent use.
Your second paragraph is based on pure speculation, and reminds me very much of Oliver Stone's film JFK in which he attempted to explain who benefited from Kennedy's assassination and then used that to "prove" the conspiracy by working backwards. This is again very predictable conspiracy theorist behavior.
NC Commish, I don't believe that most conspiracy theories emerge without motivation. I think this particular one is really no different, in formation, from the JFK theory, or the Truther theory, or the Birther theory, or dozens of others I could name. It would not shock me if the main reason you don't believe Assad used these weapons is that you don't want to believe that Assad used these weapons, because it may lead to responses on our part that you don't want to see occur. And in writing this I do not mean to be insulting, since I am often, perhaps much more than you, just as guilty of cognitive dissonance when it comes to putting aside unpleasant facts that I do not wish to accept.