"But he was also completely bonkers. Mad as a hatter."
“No great mind has ever existed without a touch of madness.” -- Aristotle
"Power the world with six towers..., no."
Perfectly possible, but would be hugely wasteful of energy. Maybe one day when we have abundant energy, but I suspect even then we would like efficiency, except for a few things where convenience is more important. For now we use the technology to transfer power between sealed sections of UK submarines, and a previous gen of the technology is used in those "wireless charging" mats.
"'Knock down a building with a small clockwork mechanism...', no."
The theory of resonance is quite well understood now, and a powerful enough mechanism could knock down a building if the correct resonant frequency was found.
Building a small compact mechanism that can do it is tricky, but I don't think there has been much study into it. Primarily because if you want to knock down a building, you might as well skip the intricate clockwork mechanism, and brute force it with a seismic bomb.