After issuing due notice to gthe opposite party/police file a Writ of Mandamus seeking directions tothe police to register a fresh FIR submit accurate reports by IO and if necessary by changing the IO as they are falsifying reports.Also pray that direct police to initiate action against the true culprits after thorough investigation.
In my opinion, you can also move an application to the judicial magistrate of your district u/s 156(3) of CrPC and let him in on all the details including the unwillingness of the Sub-Inspector to conduct proper investigation.