Is there any particular reason you "intuitively" believe demons fathered people? Didn't you say in another thread that spirits can't directly impact the physical world? Do you not believe demons are spirits?
I actually believe in the view that everything has devolved (involution): from God down to heavenly hosts down to angels down to demons down to humans. This is the most ancient view in recorded human history.
First of all, now that we got something straight here, you believe that the Essenes believed the book of Enoch, which has a passage about the Nephilim. Well, now you know that what the book of Enoch really has was not that humans descend from demons, but that the Nephilim descended from demons, which seem to be quickly extinct by the flood. If you know of any other source by the Essenes that would prove your case though, it would be interesting to hear, but I doubt it.
Second of all, considering that you misunderstood the source from the book of Enoch, how do you know that involution was the most ancient belief? What records or writings do you have that prove this? How do you know you're not misunderstanding what you're reading (or better yet, reading into something written that's not really meant).
PS One Ethiopian poster here actually showed us how the passage from the book of Enoch is interpreted differently, and that it's possible that the interpretation may even exclude any demonic descent of any creature at all.