3) must be from Quran or Sunnah
4) The person must not say it silently that others could not hear him
yes it must be from the Quran but you're missing the point, it is still called Ruqyah, it is still 'incantation' except it is the Quran being used instead of other words.
incantation=magic=spells
don't get offened...these other people think of terms like magic/spells in a negative context but Islam defines what's allowable and what isn't.
so if it contains NO shirk and NO evil/harm in it then it is permissable.
As a muslim you should be confident and open minded when you hear of things you assume are 'occult' by determining whether they contain shirk or the potential of shirk, or harm. We have been given the difference between right and wrong in clear terms.
For example, I personally find astrology to be interesting. It can explain a person's personality traits and their dominant humor/season which matters in unani medicine/healing. However I don't go around believing it determines everything in my life because astrology affects our lower bodies/lower planes. If I was at my desk I'd love no toy to something a Hindu said about this topic and it was the same view ad my own where he said we have to rise above these influences through faith in God. You might find it hard to believe but the Vedanta Hindus are the closest thing to islam and in their books actually do look down on polythiesm.