Obviously I'm a little biased, so I'll try as much as possible to stick to the facts.
Violence against Hindus in Pakistan increases due to the rise of Taliban insurgency. While the Quran says that people of the book should be treated with respect, that same respect is not given to Hindus. Also these Hindus would be forced to obey Islamic laws.
If Kashmir were to go to India (which technically it's never left), Muslims would not have to be put under Hindu law because of the much more secular government, and if they wanted to, the state of Kashmiri could instill its own laws based off of Islam.
What is a State? The idea of a nationhood is a very European concept. India has been divided on so many different levels, such as language and household deities. Europeans created India as a completely unified nation and now Europeans have also given it up. Hindu philosophy has never given much emphasis on large nationhood. India, before European intervention, was comprised of many different kingdoms. In my opinion, the world is moving towards Unions, and I think India more or less has been a successful attempt as a democratic union. So while Tamil Nadu belongs to Tamils (basically as if Louisiana belonged to us instead of the U.S. to a greater extent that it does now), it is a part of the Indian Union as well. I think Kashmir too can belong to Kashmiri people first, and to the Indian union later. Again, as Kashmir is already a part of the Indian state, the very question of Kashmir belonging to Pakistan is pointless.