You've extrapolated a lot from the statement that the pineal gland is a third eye, that is what you use to pray, and that Fluoride prevents this.
But this isn't true, it's based on what some european philosophers said a few hundred years ago, and has no basis in Science. The pineal gland is actually an endocrine gland (ie a structure that secretes hormones into the blood), it's exact function isn't yet completely understood, but it is known to secrete melatonin and is thought play a role in regulating the pituitary gland.
So it is not a "third eye", and there is no basis that it plays any role in the things you mentioned (memory, creativity and whatnot). Those things are handled by your nervous system, not your endocrine system.
https://www.ummah.com/forum/forum/islam/jinns-ruqya-unseen/485371-third-eye-haram-halal