Three things about attack-move:
You don't actually stop at the max range unless you have LoS on the target.
True, which is why spotting is so important, still not a reason to not use atk move considering that manually halting and targeting an enemy unit doesnt yield better results.
Also sometimes I notice that tanks sometimes creep up to closer than max range.
Entirely reliant on the deceleration of the tank. Some tanks are better at stopping then others. Hitting halt instead of atk move is not gonna make your tank stop any faster.
Attack-move doesn't consider the range buffs you get (sniper vet 3 or CCT for your Firefly) so you end up going back to normal range.
Yes it does. Only limitation atk move considers is whether or not the target is within LOS.
If you have LOS and the range to hit the target, the tank will stop at that range (or close to it) and fire.
You can't target specific units with attack-move.
Its a gambit, but mostly the targeting priorities get things right. Which is why i put in my original statement that atk move is useful "95% of the time."
I know fully well that this isnt the case for some vehicles.
An example of this is that pretty much every allied tank will target a P4 IST over a 50mm halftrack because P4 armor is read by the game as a more dangerous tank, when the 50mm HT is far more deadly. This is one of those situations where you physically target over using atk move.