Chayba don't pretend to understand astrophysics; you don't.

Dark matter and dark energy are a conceptual kind of matter which do not interact with electromagnetism (so are not easily observed). They are a mathematical necessity to explain the anomalous rotational speeds of galaxies and other phenomena, as they would provide extra gravitational force. There's about 74% dark energy and 22% dark matter in the universe.

The aether has been completely disproved. The Michelson-Morely experiment did this over 100 years ago. Einstein's theories of relativity were then developed in order to be consistent with a lack of aether; there are only relative positions in space. There is no immobile aether in which everything has an absolute position.