1)you must immediately with draw the power of attorney given to your ex BIL
2) issue notice to BIL that POA executed in his favour has been revoked
3) issue public notice in local newspaper that POA has been revoked
4) if your POA has been with drawn then for property transfer your personal presence would be necessary
5) sub registrar would insist on your personal presence with identity proof ie your PAN card
6) if your husband signs your name on the documents he would be committing the offence of forgery which i doubt he would do
7) you can file suit for partition to claim your 50 per cent share in property in india