1)as on date your husband is co owner of the house . he has 50%share in the said property .
2) your husband/ mother in law can execute gift deed in your favour .
3) it would attract stamp duty as well as registration charges . actual cost would depend upon market value of the house as well as stamp duty charges levied in kerala
4) will is the best option . your husband can bequeath house to you under will . sign the will in presence of 2 attesting witnesses . no stamp duty is payable on will .
5)in event your husband dies intestate ie without a will his 50%share would devolve on you , your mother in law . i presume you dont have any children .