In my opinion, as long as Pakistan is still semi US ally, selling J-35 and other advance tech to them would be very irresponsible.
Plus the unintended consequences of pushing India into upgrading/joining the F-35 camp.
Even selling J-35 to Egypt is risky since it might up in Western hands. Iran as well; they have too much Israeli infiltration within.
Unless Pakistan establishes very close military relationship with China--ie naval port or bases in Pakistan--or India acquires 5th gen (not likely for a very long time), PLA should hold off from exporting to them.