SSH is a limit HE book. If you are playing NL, you are going to have to take a lot of the hands that is ok to play in a limit game and throw them in the garbage.

Your pattern recognizer is what you are talking about. SSH hold 'em does mention this and how critical it is to stop it, but unfortunately, gives no real recommendations on how to do so.

The best way to keep your pattern recognizer in check is to avoid playing marginal and crappy hands in the first place. If you don't give your pattern recognizer a chance to run wild, it won't. As far as negative effect on your premium hands like KK. You are right, it's your sample size. Have faith in the mathical probability that KK is going to win you money in the long run. With a bad run like you've had with it, it's going to take a while for you to get +EV out of KK but it will come with enough hands.