I don't think people here are asking the right questions.
1) For the sake of argument, let's assume the lack of spares from the U.S is true. Is this only restricted to f-16s alone? Pakistan uses several US hardware. What about those?
2) Let's assume suspension of spare parts is false and all US weaponry is battle ready. Can Pakistan use it on any adversary?
3) Given the current scenario, will the US allow upgrades to the equipment to keep them current?
Even if any of 1, 2 or 3 is true, Pakistan has just thrown a serious advantage not counting the cash it has spent, down the drain. Pakistan needs to mend it's ties with the US and while doing so think of diversifying it;s critical equipment.
Lastly, Pakistan, China and Russia may or may not form a partnership but when it comes to weapon sales, China and Russia is more a competition than partnership. Any country would love this situation and would happily over price it's equipment.
Mend your situation with the US while you think of plan B. That is the only prudent way of moving forward.