Why is the Dark scary?

[cafolini]

Because animals come out to hunt at dusk and because we humans can't see **** in the dark.

Next I'll settle once and for all the body/soul dichotomy and the matter of free will.

I think you are correct to an extent there. The dichotomy and free will will have to be settle after the recognition of inabilities to have full choices. Then free will ceases to be a genuine consideration and what's left is freedom of choice within a subset of probabilities. We have no other road outside of fantasy.
Yet, the variables are so staggering that it is often impossible to eliminate fantasy no matter how much knolwdge is possible. And also what has to be considered are the new technologies springing from thermodynamics when it comes to vision.