I am not certain, and that borders on the dreaded SSI region, so I hate to say it, but I can't (and if I could, I wouldn't) answer that one.
1. Not always, depends on how much is there.
2. Nope.
3. Not always.
4. Carbon fiber can be a threat to the passengers. Only after they are screened by the x-ray.
5. It is simply clearing the collar of threats.
6. Applying the rules as equally as possible (I know, there are exeptions, and I dislike them, but I don't make the rules) is not implying we do not trust folks, it is merely establishing a baseline of security.
I
HATE that phrase more than you could ever imagine. It is nothing but a phrase that escalates a minor miscommunication into a full blown crap sandwich. If I were Administrator, the first rule I would make would be to ban that from being used in any checkpoint (or anywhere TSA is working) under penalty of being fired immediately. If passengers are simply talking or even (gasp) joking around with us, there is no reason to get worked up. Sadly, that does not seem to be a consensus.
If that is your hair, I have no reason to pat it down, it can be cleared visually. If you look just like Ellen Barkin, why are you here typing with us and not in movies?
I can get enough C-4 in a collar to kill a handful, injure more and if I were able to put it at a critical juncture, maybe cause some pretty bad damage - but not a critical or catastrophic failure. Too many variables to give a definite, but I doubt I could bring it down or blow it completely out of the air.
Yes you can bring a set of extra guitar strings, and they make nice garrotes if you have a couple of thick wooden pegs (to prevent you from hurting your hands in the process).