Marriage Separation

I, a widower at age 65 married a widow of 56 years in 2011 but not registered and unconsummated. Life had been a hell in the last 4 years and she has a son born in America and an American citizen and now aged 36.and married and well off but he does not want his widowed mother in US and my son is also married and was outside India for 10 years and now he has come back but my wife is not willing to live with them. and says that she will stay in our ancestral house and that my son, his wife and his child and if I want I can also leave this house and she will stay here. She has a property worth Rs 70 / 80 lakhs and want a share of my property whereas I am in debt after this marriage. Her son can easily support her financially. She also earns in part time but not much. I have a fixed pension of Rs 8000/- p.m. I or my family members cannot live with her anymore. Please advise if we have a separation agreement or should we go for divorce and how long it will take to get a divorce and what is the cost implication. Pl guide and thank you so much for your help. God Bless You All.