Hindus are a minority in Punjab, and Sikhs are dominant. At the time when the Jatt Sikh militancy broke out, Punjab was one of India's richest states with the politics and the economy being "dominated" by the Jat Sikhs. While Punjab's economy is a shadow of those times, it is still "dominated" by Jatt Sikhs.
https://books.google.co.in/books?id=iNBbBAAAQBAJ&lpg=PT11&ot...
I think I've already answered that India's Sikhs don't want anything to do with Khalistan. As to why, the answer is simple: without the rest of India and it's unified market and the rights available to citizens, Punjab will be an economic basket case, as would almost any other Indian state. Not to mention they will certainly be cut off from their temples and monuments established in other parts of the country. Communities established in the rest of the country will be likely forcibly expelled to the new state.
(Edit: I'm not wishing this would happen. But given India's history with partition on religious grounds, this kind of displacement on a more thorough scale is exactly what is going to happen. My argument is that Sikhs and every community knows this, and that is why I have pointed out that it was the Sikhs who fought the Khalistanis and either eliminated or drove them away)
It is only a small section of Commonwealth Sikhs who use this Khalistan thing as a cover for their criminal activities. One only needs to examine the circumstances in which these "activists" left India and the present company they keep to realise this. It is possible some of them are still rightfully pissed off about the raid on the Golden Temple in '84. But formation of Khalistan does not serve their interests.