You keep adding to your post while I am typing LOL!

No I don't believe a poltergeist is a mere mental suggestion. I do believe a poltergeist is unconsciously a creation of a person. Just because we don't understand how it happens, doesn't mean that it can't. Poltergeist cases that don't involve possession can still feature all the things you listed. There is a lot of evidence that psychics and mystics can do some of these things consciously too. I think the human mind is capable of things that we barely even dream of.