1 - We all are parts of the universe. If we are not composed of matter as you imply, probably we all are only bags of air floating in space.
2 - Energy, time, space, motion, light, heat, etc, all all accidents of matter. If matter did not exist, none of those accidents would ever happen.
3 - Existence of what, energy or matter? I think you are the one creating the mystery.
4 - I do know what the origin of energy is: Matter. Were not for matter, there would be no origin of energy.
5 - I call it matter. Only that it was caused by something else albeit no derived from matter that preceded it.
6 - Yes, only in the mind of the one who can't think logically.
7 - I have told you above that I do. Hence, the mystery is no longer a mystery to me but as I have just said, only to those who can't think logically.