The real world is seldom as simple as the maths, but several animals do see much better than humans. In particular hunting birds.
A biologist might have to chime in on this one, as it might genuinely come down to rod/cone density and other factors as well.
I mean, there is magic in lord of the rings, so I’m sure their physics and chemistry systems have some oddities that our world does not
I think yes (just use lamda/n in place of lamda). I seem to remember diamond has one of the highest n in visible (while still transparent), so it might be difficult to imagine it could be higher than that. Alternatively, why not say Legolas can see in the ultraviolet to get lamda down.
The Airy disk is caused by diffraction at the entrance pupil to the lens. Even a perfect lens would be affected. The vitreous humor (which is behind the lens) cannot restore image degradation that already occurred when light passed the pupil.
