1) Whether it is chemistry or political science; the researcher has to always ensure that the basic input is accurate. "Garbage in, Garbage out" applies to ALL scientific endeavors.

2) Appeals to authority are only fallacious under certain circumstances. In this case the CIA has used his services and compared them to their own analysts. The results have a direct relation to the topic of the article...ergo it is not an "empty" or fallacious appeal to authority.

3) The article refers to PS, the PEER REVIEWED journal of the American Political Science Association and the premeir journal of the discipline in the US (an equivalent to the New England Journal of Medicine or any other peer reviewed academic journal). So to answer your questions: these methods have been and continuously are tested within the discipline.

Finally, remember this is a e-magazine article with popular appeal...not an academic journal. It is not going to give you all the technical specifics. If you want that you need to dig deeper than a journalistic article that only scratches the surface of the topic at hand.