Wife's Attitude

you must file an application for act and conduct of your wife before the SSP of your area.

another same application may be file to woman cell.

you must also inform your  in- laws  about the behavour of their daughter

He can write to the police about the said threats given by the wife requesting them to take steps against her.

in my view the husband should report to police authorities regarding such threats as the definition of mental torture dastane v/s dastane 1967 sc matter landmark judegement on issue of cruelty by wife in matrimonial  dispute

I agree with Mr.Rajendrasharma, but even after complaining to police, if some thing happens, you should prove yourself. Unless, you have clear evidence in this situation, you cannot prove any thing against her. First try to get some evidence by audio /Video recording of her threatening patiently. Then approach Court thru private complaint which eventually forwarded to Police, Take your child into your custody and keep her away from you and your child.