Thank you for sharing that. But there is a different perspective of the “physics” if you are interested in exploring it?
What if they are not actually physically moving to travel? But instead they can just change their static location in Space/Time? If they are as advanced as I am guessing, they have mastered and utilized the entanglement theory of Quantum Physics and Space Time. And just like the proverbial StarTrek Transporter they can just wrap themselves into a package and then just relocate that package to a new location millions of light years away in a few seconds without physically traveling those miles and dangers.
So in other words when we see them darting around in the sky they are not physically moving at all and none of standard motion physics like inertia and G forces apply. They are gently manipulating space time within our own linear timeline to give us the optical illusion and visual perspective they are physically moving one direction or another. This would explain why they can move so fast and change directions so fast without turning themselves into liquid against the inside of their craft.
The more we learn about particle physics the more this appears to be a possibility. I think we are right now on the edge of discovering how the spooky entangled particles operate with dark energy/vacuum energy. We know the particles pop up from nowhere and then disappear again to who knows where. But I have a theory that they are not just relocating from place to place, or being created and then destroyed. I think they are a fog of particles that move all over the place in Space Time but are still all entangled with others in Space Time.
So if this Space Time particle energy could be harnessed, the control of Space Time I described above would absolutely be possible. And the physical forces of inertia and gravity would not apply. Not even linear time would apply... Here one minute there the next... And somewhere in the past, or in the present, or in the future. Just like dark vacuum energy particles do. Just have to make the principle universally apply to the whole package you are transporting through Space Time.
As for your second point about demons. There are always opposites in everything. When there is dark there also has to be an opposite light. Or you do not even have anything to gauge and compare the dark against... There is always up or down, hot or cold, left or right, loud or quiet, positive or negative, Male or female, Etc. Everything has an opposite. So with these entities there are both dark and light. One cannot exist without the opposite other to compare them against.
Some of what you discussed here sounds a lot like the Alcubierre drive:
https://en.m.wikipedia.org/wiki/Alcubierre_drive
So they’re updating their xyz coordinates. Always wondered why Neo didn’t do that to save Trinity