I'm guessing Sukhoi, but I bet the F-16's were promised to Pakistani from day one for their help in Afganistan. They wanted and needed F-16 spares so badly before 9/11 that I can't believe the issue wouldn't have come up from the start.
Yep,that's the most logical reason.Besides,gifts can also be used to encourage behaviour along expected lines,if not for rewards.Pakistan's record on nuclear proliferation & shutting down of terror groups hasn't been too satisfactory.Though I doubt things will drastically change with the military in power.