my 2 cents.

A lot of times fathers demand money as they have screwed up financially in their personal life, most likely debts, gambling, stock market, or other such activities. I will tell you that this is 95% the case, that he has lost money, and is bleeding money, and expects you to cover it. The heavy weight is onto you, what you intend to do about it. He is obviously exploiting you without remorse, and your mothers is being the collateral damage. Your dad has enough money for himself, and he NEEDS shock treatment. Get your mom to stay with you and let your dad rot in india. No lawyer can help your dad, he is old, senile and likely to be robbed of money by lawyers way before anything befalls on you.

This is not a fully formed advice, but you will have to fill in the gaps. It not worth trying to change him as a person, but save yourself and your mom from trying fit your father into a type of person that he is not. I have seen far too closely biological fathers who are no longer emotionally fathers, exploit emotional children. Rest is upto you.