Answer:
Yes, that is correct, 120° and 60° are the most widely used supplementary angles.
The answer is that "since they do not interact with the electromagnetic force, they do not feel friction or drag and hence do not contract with the rest of the protogalactic cloud." WIMPs (Weakly-Interacting Massive Particles) are hypothetically constituted to dark matter. It is in their nature to be less interactive, so they are scattered throughout galactic halos and not focused into the galaxy's disk.
