Property registry cancellation

Dear All, my father sold property on 3-11-2016, few days before demonisation. before registry he gave us 55 lacks rupees in which 35 lacks through cheque that is mentioned in registry and 20 lacks in cash. the total amount of registry is 2.80 cr. rest amount was due with post dated cheques on dated 31st december, 14 january, like that. we submitted both cheques two times and got bounced. After which we sent him legal notice then any how he gave 25lacks amount on behalf of 14 january cheque. all cheques are mention in registry with cheque no. and other details. now cheque validity of 50 lacks cheque is over and payment is still due. After that we chased him then buyer is telling he'll give through RTGS and now he is tolerating day by day. my father files case on him with section 138.(cheque bounce) we've given application to prevent mutation untill full payment is due. Dear All, kindly give suggestion what should we do now to strengthen my case?? 1. can we do FIR against