That’s not a book I’m familiar with, so it’s difficult to answer without context–but I think you’re asking an earlier question in with slightly different words.

You could say it was ultimately Malchut. “Light and darkness” which “light” is His essence, already existing, and “darkness” is as the will to receive–although there are “stages” before the revelation of Malchut which are included in the final day as well.

No distinction in importance.

See answer below.

Emotional.

The focus should be on changing the heart. If the mind serves the heart, the mind is at the same level. A higher force must lift us to a higher mind and heart. The need for this ascension depends on our lack that we present for that higher degree–the quality of bestowal.

All of reality is how the vessel feels the light.