Pakistan supported Taliban because Pakistan wanted to ensure that its rear-guard (Western border) was relatively secure. This was the calculation made then based on the assessment on the ground.
As to why Taliban and India are mending fences, it is because of the former's need to gain greater acceptance and the latter's need to keep Pakistan on its toes.
What is IAF and why would we support it? I am not sure what you are alluding to.
Terrorism emanates from outside (and whether civilian or military government, they have all had to fend it off). As an example, ZAB started the campaign against Baloch terrorism and because of the geo-pol, this will continue. Same goes for India in IoK etc. etc.
I have written this multiple times, Afghanistan will not rest easy till they have all of KP. This is the reality of the situation. Second, India will continue to support terrorism against Pakistan because it is their state policy for as long as Pakistan does not surrender its claim on Kashmir.
So if you want to get rid of terrorists, you have one of two options. Take your pick. Your majoritarian PTI rule cannot add another to these options.
a) Surrender Pakistan's stance on Kashmir and accept India's dominion over it. Plus, let Afghanistan decide the fate of Durand Line as they see fit. These two will IMMEDIATELY lead to reduction of terrorism inside of Pakistan.
b) Fight the terrorists and their foreign abettors and pay with blood and treasure.
There is no middle ground. PTI/IK are not going to get the Afghan government to stop supporting TTP in its quest for imposition of their version of nizam inside Pakistan. Similarly, IK/PTI can do nothing but to take on India as the current and past governments have done.
So you can sit there and curse the policies of the past and blame them all on Khaki, as is your prerogative, but you have nothing better to offer.
There is not one post here from any of the Army bashers to state with clarity, what their solution for addressing terrorism inside of Pakistan is.