Answer:
(Fatwa: 342/46/TH=1431)
You can never marry your sister in law keeping your wife in nikah, it is invalid and haram. Also, it is major and haram to have intimate relations, openness and seclusion with her. You should immediately severe your relations with her and repent to Allah sincerely. Stay careful in future and keep on fulfilling the right of wife fully. You were deceived by the nafs and Satan that severance of relation with her and her valid Nikah will create troubles for her. The only way to protect for both of you is to pay attention to rectify yourselves.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
