But that "something" keeps being pulled down until it is stopped/blocked by something (e.g. the ground). Gravity is perpetual relative to the source of the gravity. It's just that our surroundings change and give the illusion of gravity changing...i.e. we don't "run low" on gravity
I don't think Maxwell's Demon is 100% solved.
Tidal energy could play into it, some underwater tides deep in the ocean are insanely strong.
You're confusing force with work. Gravity is a perpetual force, but a force doesn't generate energy.
To generate power you need gravity to move something downwards, releasing the potential energy. And when that thing hits the bottom of the shaft you've used up all the potential every that was stored in it.
I don't think Maxwell's Demon is 100% solved.
Tidal energy could play into it, some underwater tides deep in the ocean are insanely strong.