Difficult to say. If I were to venture a guess, I'd say anywhere between 300-900 m. That's just my guess.
Pretty darn good. How do you think they got the video ? Here is what I think happened :
The sniper-spotter team located an enemy hideout. Given how relaxed the enemy is I'd say they were a bit deeper into enemy territory. The team got into position. The spotter either switched from his spotting scope to a DSLR camera or attached some form of a camera to the spotting scope itself. Given how we also have audio, I'd say it was a DSLR camera with a mic attachment.
Then they would've waited to record enemy movement and to find an opportune moment to shoot. When the targets lined up in a single file the shooter opened fire. Now the first shot of a sniper is usually the most inaccurate one, it is called the cold shot. It is inaccurate because of improper reading of environmental variables which is actually quite common. Here the cold shot took out 2 guys with a double head shot. That's incredible ! Sure the follow up shots were a bit less organised than ideal but keep in mind this wasn't a SF unit. These were regular infantry guys from the Maratha regiment. This is a good reflection on the training general infantry receives.
They did all of this and the Pakistanis didn't know till too late. Better yet they had time for a : "3....2.....1..Chatrapati Shivaji Maharaj ki JAI". Premium quality trolling this.