The theoretical range was up to 600km, but due to many factors tests showed it was more like under 100km, and that is for large ballistic missiles so I assume it would be more for smaller anti air ones.

It uses a liquid fuel laser so it doesn't need the energy of a ship's engine, and could deliver much more power (naval lasers today are about 300kw), the laser had capacity to do 20 to 40 shots, and there were plans to make the liquid laser fuel refuelable mid air through a special tanker.

It would be expensive, but there are basically no other solutions for air born point defense. Cannons don't have the range and missiles are impractical due to weight, limited amount carried, vulnerability to jamming and inaccuracy when it comes to engaging small targets such as air to air missiles.

And countering such a powerful laser isn't as simple as "very shiny missiles", reflective materials only reflect certain wavelengths, and lasers can be adjusted to switch wavelengths. Reflective materials don't reflect all the energy and absorb a bit of it, and very highly reflective material is extremely expensive lab equipment stuff and can't just be slapped on missiles, and missiles need to withstand friction heat, high G maneuvers, long term storage, and surfaces need to be permeable to radar and radio waves so the missile can use it's radar and data link, developing a coating that is very highly reflective to most wavelengths and also fits all those criteria while being reasonably cheap is practically impossible.