I have this deck, but have only had the chance to read with it a few times. I find that it is a lengthy process, and that the cards have a lot to say when I use them. I usually need about an hour or more to journal out everything that comes from the reading.
I have noticed a sense of a presence around me when I use the deck, sort of like being under a magnifying glass, and I am reminded of how tiny I am. But nothing more involved, only when I read the cards.
I am not sure why you are feeling disturbed sleep and such while using the deck, I have found the beings related to the cards to be cautious, and slow to act, but not evil or malevolent.
What sort of upbringing do you have? Oftentimes, when someone grows up with a religious background that espouses fear towards demons and the "wrongness" of dealing with them, that brings emotions into the person's life that cast shadows that cause more fear. I had to overcome similar feelings when I left my birth religion for Paganism and Witchcraft, but once I discarded the mentality that I was going to hell, I overcame that fear and was able to grow in my beliefs.
It could be that you are experiencing the same sort of feelings, arising from conflict with beliefs that are fomenting more fear after having used the cards.
For the connection between Demons and Fae, I feel that Fae are much different (nature spirits, connected to elements, originating from wilderness, etc.), where Demons seem to be more connected with Ceremony and Ritualized contact. I don't know where either has originated from, but I find that they are two different sets of entities.
Does that make sense?