By "rational strategy", I mean one that results in the best outcome for the person (most utility, less jail time, etc.) With your "rational strategy" of ALL-Defect, the person is almost minimizing his utility. That's not rational. Yes, it "beats" the TFT guy, but that's not the goal. The goal is to maximize your own utility/happiness, not "beat the other guy".

Your TFT-1, TFT-2, ... scenario will not be played out by the rational person. Again, the rational person knows that if he defects on the next to last round, the TFT guy will defect on the last round, thus the next-to-last-round defectgor ends up not maximizing his utility, SO he will NOT defect on the next-to-last round. They both might defect on the last round, unless there will be multiple games played with multiple people, and they know you defected on the last round -- there will be retribution to pay -- as no game is really "in a bubble", and previous games will affect subsequent games. Again, maximization strategy is to cooperate -- and use TFT to communicate your strategy.