Filing Mental Harassment - Against my ex-wife

In January this year, me and my ex-wife have been divorced with mutual consent under Muslim Shariat Law with the help of All India Muslim Personal Law Board in presence of witnesses. Mehar, Iddat amount and Goods exchange has already been done amicably. Maintenance amount for my minor son has also been decided which i am ready to pay. In May I received noticed from her through lawyer demanding several things along with 25 lakh rupees, they have threatened me that failing to fulfill their unjustified demands will lead to prosecution against me under 498A, DV and several other acts. After 4 months of divorce, sending this notice and asking for hefty amount and threatening for falsely framing me under 498A and DV was just with the intention on harassment and extortion. Being an Indian Citizen do I have right to file a Mental Harassment Case against my ex-wife in such a scenario? If yes, then what's the procedure? Also, while having a divorce we had signed and agreed that after our divorce we will prosecute each other in any of the court as all our matter has been resolved amicably. This document was signed in premises of All India Muslim Personal Law Board and in presence of witnesses . So, can I file Breach of Trust/Agreement in such case? If yes, then whats the procedure?