300:
Not sure what you are looking for. Clearly since a bunch have read the post and no one has responded, either there are no clear keys users, advocates or dissenters among them, or they aren't willing to try to answer the way you asked the questions. I guess I'm not the right one to respond, but will make a couple of suggestions.
First, your questions are all "closed" ones, except for the last one, though by the time one gets there all that's been available for rresponse is a "yes" or a "no." It's hard to build a summary, as your last questions wants, on "yes or "no." When you say SPECIFICALLY, you give emphasis to a word which is likely to chase any responders away unless you happen to encounter someone with a lot of experience.
If you are truly interested, I'll give you a challenge: buy the book, read it and work faithfully with the principles. If it doesn't improve your game, I'll give you twice your money back.
But, be aware that clear keys will not help you with pre-shot planning. Pre-shot is manual. Clear keys are the tool for automatic. A solid pre-shot, however, is mandatory for working with a clear key, which is the managment tool for playing the game on automatic. Pre-shot doesn't need clear key. Clear key needs sound pre-shot. Guaranteed, you will not be able to play on automatic without clear keys or that very same principle under some other name (And I have not seen such a resource up to this time).
As one who has used them for 20 years, I can say "yes," to number 2 and number three, and "no" to number one, but having developed a strong sense of pre-shot planning, number one helps me with the automatic function, for which clear key is no more or less than the management tool.
You may also want to see what some others who have used clear keys have to say, which you will find on my website. Maybe someone can come up with a better way to kick a "one-shot" 40 yard field goal in front of a Peach Bowl crowd worth 250 grand. Just ask the guy who did in with a clear key - just like he plays his golf.
Finally, I will suggest that anyone who uses clear keys either half heartedly, or with a negative, prove-it-to-me attitude, will likely fail. The entire process involves important knowledge that is long since tested, demonstrated and validated. It's not apt to be accepted by anyone who doubts that kind of evidence. Trust comes first. And there is no half-way house for clear key users. It's all or nothing - or at least very little.