How to claim interim maintenance from husband

I m married since last 17 yrs with one girl child of 8 yrs and 9 months pregnant with other.My husband is not ready to give me monthly expenses since last two months.Moreover he is not ready look after our kid nor me....He is emotionally and mentally harrassing me since long time.He not coming home to speak face to face and running around ..His parents also saying do whatever u want to and supporting him who r living in village......He is working with merchant navy and has salary of 7 lac and other his owned 4 properties which mkt value is almost 4 cr in his name including this house we staying.I want to know how much interim maintenance can I expect? Also I want to know what r court stamp duty cost for the same ? In how much time can i expect interim maintenance will start as my delivery date is due but i have no money for that nor for daughters school admission...??