1. Any advocate in India can make the power of attorney as desired and the same should be signed by your father in law and should be sent to you for signature as well as for the integration by the Indian Consulate in the country you are living in the consulate charges fees for the authentication of the document that you will know only from the consulate.
2. Yes power of attorney should be registered in India and register charges will be around rupees 10000
3. For making power of attorney no stamp duty is payable accepted the stamp used for making of power of attorney you have to pay only that authentication charges in the Indian consulate and registration charges at the local Registrar office