One of the better parts of what he does is describing how they can do the "terminator goes back, and then the good guy goes back" scenario. Terminator fails to kill John, but accomplishes something else that John doesn't like. John then sends the good guy back NOT to save him (he's alive, therefore doesn't need saving in the past), but to protect Sarah.
The only problem is that there's no way Sarah would've ever gotten away from the Terminator without Kyle's help considering what we see in the movie. Plus, it clearly wasn't intended to be that way.
MJ Young's theory has plenty of holes in it, and is mostly just an attempt for him to sell books. Notice he does say that T3 doesn't work with his theory. T4 wouldn't either, since the movie itself has very little to do with logic.