The problem with intelligence reports is that they are primarily based on hearsay, conjecture etc, evidence that would never be admissible in a court of law. A lot of the time it involves analysis based on extrapolation from minor or unrelated/indirectly related events, and can be subject to various "agendas" and/or biases (inherent or otherwise). "Testimony" from individuals who have been "captured", given the attitudes of our LEA's, could very likely be coerced or obtained under torture. We saw this in the run up to the Iraq war, with a motley of different intelligence reports from different parts of the world patched together to make a case for war that was sold pretty successfully, but was nonetheless highly inaccurate.
With reports from Indian quarters, it can be argued that the suspicion, of biases and prejudices against Pakistan being a primary motivation for implicating its agencies (in events outside Kashmir), is a valid one. I have doubts about the accuracy of reports implicating Pakistan that originate from the West as well. The "think tanks" and "councils of this and that" probably have a lot less "hands on" intel than do the Indians. The majority of those reports probably start of with Indian reports as a basis, so the objectivity/accuracy is already compromised.
Is it possible that Pakistani "moral" support for the freedom movement in Kashmir is diverted to other locations? Of course, but the actions of the militants in Pakistan has shown that there is no dearth of sophisticated weapons and explosives for these groups even when the state is not supporting them.