cancellation of sanad

if the settlement is legal then you cant apply for cancellation his sanad as most of the matrimonial disputes settled outside and that is appropriate also since trial takes much time to dispose of the case. but he is extorting money and you have strong enough supportive evidences then only you can report his behaviour at the concern bar council.

merely because your in law filed or got filed DV and 498 case, you cannot try to cancell his sanad.  If you are having cogent evidence and documents, you can file a complaint before the appropriate bar council for appropriate action.      

his signature as a lawyer in  "vakalatnama" of your 1st divorce case is a good piece of evidence that he was aware of everything about you.under indian evidence act it is admissible in the courts of law also.you must have to engage a good lawyer for that . Don't this at your own as you are taking action against a person of law protection machinery i.e.lawyer hence it would become a serious issue if your evidences are weak.