Infinite km assuming nothing gets in its way. On the other hand, the beam "diverges" - gets larger over distance. Therefore at a few km it may be meters wide and not look particularly laser-like.
In either case though, there's no way to tell you it can point X kilometers unless we are just pulling a number out of our... hat, sorry! Science sure can get frustrating at times .
(a good rule of thumb is that, assuming nothing blocks it, 1mW of laser light can travel infinite meters, so you can multiple your mWage by infinity to determine the laser's "range" [in meters!])
Yep,
Pretty much you have two BIG enemies fighting the range of your laser beam in nature.
#1 Divergence of its beam. It will ALWAYS GROW (spread out), and the projected dot will turn into something big that you don't want to admit your laser is outputing
You'll have to work hard to limit its growth to minimum with best possible optic sets.
#2 power of photons outputted will be induced into medium (air/atmosphere) and scattered (reflected around) off the particles and molecules of the medium. That prevents your laser's beam from reaching further forward.
There is #3 but I'm too drunk and tired to support it .
I'm sure someone will kick in with the rest.