Your analysis of Pak-China relationship is, for the most part, sound. However, some of the following points would merit revision:
Inclusion of the importance of Hargos free trade area and the benefits Pak can acquire as a result of the eventuality, how Pakistan can link its exports of products with Chinese supply networks and how the $104bn Xinjiang economy can be made to work for the interests of the country---all of that in the economic realm.
In defence, also mention the increasing cooperation that pak has with china in the production of missile technology.
These are some corrections:
U.S wants to keep its stronghold in asia, even after the cold war. The invasion of Afghanistan in the post 9/11 incident was a continuation of its imperialistic designs---a bit of a sweeping statement, considering the fact that it has been a security war.
With this ambition, it has joined hands with india, japan and north korea--It cannot be North Korea which has been branded an axis of evil by the Bush admin. If you are referring to South Korea, that is ok.
Also, a point that is conspicuous by its absence is the facet of the control of the maritime security of the Pacific---I think that is where US really wants to harm Chinese interests, with the connivance of Philippines, Vietnam and Japan.
All in all, your answer is still very good.