1. Does the relationship between your husband and this lady date back to the time when your marriage was not solemnized?
2. Since the FIR has been lodged the immediate priority of your husband should be to get bail, failing which he can be arrested at any time. In the absence of protective cover of bail your husband can now be arrested any moment. It may take months to obtain post arrest bail. So let your husband immediately file for anticipatory bail in the court to pre empt his arrest. Thereafter, contest the case on merits.
3. Bank transactions of money given to her by your husband do not help your husband in any manner.
4. Whatsapp messages can be used by your husband in the court subject to their content.
5. Engage a lawyer and immediately seek bail.