A) They don't seem to accept Durand Line. The fact that even Talibs (even after having support of Pakistan to run their government in Afghanistan) became hostile to you eventually, shows that Afghanistan will NEVER accept it. Though Afghanistan is weak at the moment so it can't do much right now, but whenever their situation improves, this is going to be nasty.
Luckily, Pakistan no longer cares what Afghanistan thinks.
B) Oh common, I can give you many links where Afghanistan head called Pakistan a brotherly 'country' so it's wrong to assume that they don't consider Pakistan a sovereign country. At least I believe it.
Words are meaningless, action is what matters. The fact that their official policy says that half of Pakistan belongs to Afghanistan, and the other half belongs to India, proves how much the Afghans really care about Pakistan's sovereignty; Spoiler, they don't actually care.
For the rest, I hope you aren't telling me that you provide safe havens to Talibs because the West providing shelter to Pakistani criminals, are you? If you are then it's kinda unfortunate. If you aren't, then it's fine.
I'm not, I'm simply pointing out the hypocrisy of the situation. While I don't necessarily agree with everything he says, I think former CIA official Michael Scheuer has a better understand of the situation in South Asia than most of the US government, military and intelligence services.
The only thing I'd say is this, Pakistan cannot and should not fight the Afghan war on its own soil. Pakistan may ignore the Afghan taliban, but that isn't the same thing as helping them. As it is, Pakistan has no real reason to start a war, which frankly the world's greatest super power has failed to win; you can probably understand Pakistan's reluctance here.
IMO, Pakistan support Talibs because of so called "strategic depth?" Pakistan thinks that a India friendly government in Kabul is a threat to it?
Pakistan isn't afraid of an India friendly government, Pakistan is afraid of a India controlled, anti-Pakistan government, which the successive governments in Afghanistan has been, since the ouster of the taliban.
Anyway, I firmly believe that supporting Talibs isn't gonna take you anywhere. It backfired after 9/11 and it WILL backfire again if you don't act NOW. The West don't have to think about such consequences for "supporting Pakistani criminals" but you do. Sad but true.
No, what backfired was Pakistan joining a war, which has led to a civil war within Pakistan, with tens of thousands of Pakistanis dead. If Pakistan had stayed the hell out of it, and Musharraf had told the US to **** off, Pakistan would have been in a much better position right now.
Tens of thousands of lives lost, hundreds of billions of dollars wasted, an entire generation lost to a war economy, that's the price Pakistan has paid for getting involved in an unwinnable war on terror.