Very impressive development.
Not so fast, my friend.
Pakistani ballistic missiles and cruise missiles are largely committed to strategic applications (to deliver nuclear payloads to potential targets). These are not easy to mass produce due to 'capacity constraints' which are largely overlooked in the Public discourse.
S-400 system feature several launchers and can develop fire solution for multiple targets in one go. India is also expected to complement S-400 system with additional set of defenses - layered defensive strategy.
To counter
that, Pakistan might have to subject the location of an S-400 system to a volley of ballistic missiles followed by UAV as well as introduce Ra'ad II cruise missiles in the mix. WE can take cues from the Iranian model of mass producing theater ballistic missiles (TBMs) and UAV for the needful. If this is not easy then Pakistan can try its best to make sure that the costs of waging a WAR with
it will remain very high for India for indefinite period.
If several countries (Russia; Israel; France; USA) are committed to enable India to deter China in the long term, I am not sure how strategic balance can be ensured in the region for indefinite period.
Pakistan-China duo is POTENT in theory but China have never gone out of its way to make it possible for Pakistan to defeat India in any WAR before. This might change with CPEC in the picture hopefully
but Pakistan need a bigger geopolitical clout wherein it can reach out to Turkey, USA and UK for advanced technologies. Pakistan must devise a comprehensive strategy to fix its dysfunctional economy and develop powerful connections.