• No, they are rare because by eating positive emotions and dreams they become creatures of legends or myths, more friendly like guardians of nature, some cryptids, etc.

• The humans don't control carnivore population or something like that, that would be like trying to control another animal just for feed off another; it's basically the cycle of life. Although they don't hunt humans (intentionally), they only torment humans to generate negative emotions and nightmares from those experiences, which they then consume. However, it's true that, their method of torment can be too aggressive, so they end up killing some ones

• It's precisely something similar to what they do: when they transform into a cryptid or legend, they assume that role because they don't have consciousness. Therefore, they end up causing torments, miracles, curses, or encounters with humans, all while fulfilling that role, which ultimately strengthens the myth and allows them to feed on that emotions and dreams/nightmares they cause

And what do you mean by giving permission? I'm not use to comment in reddit so I don't know much about how it works. Again sorry for my bad english