How long should I tolerate the cruelty of my wife ?

This is strange case of cruelty and black-mailing by a wife. We are married, 12 yrs now. Within six months of marriage, my wife started showing aggression by suddenly leaving the house because of a silly reason that the boundary wall of the house was too high ! Today we are living in the Metropolis and have a son, 11 yrs old. Since my father retired and they were living separately in the old city, all alone, I decided to bring in my father and mother to live with us. That was something my wife never wanted but never expressed too. However, she slowly started hatching notorious plans under the guidance of her mother, which I understood very late. She first demanded that I shud hand over the entire salary to her and she will manage all the expenses and also save money. I said, the whole salary is not possible since I have to keep sufficient amount in my account to pay various bills online. I started giving her sufficient amount, every month, so that she could manage the house expenses. Since, last few years my parents started complaining me that they are not getting good food to eat and is being treated very badly by my wife, especially when I am out for office or some official tour. Both my parents have become very ill and they have multiple medical problems. However, being a retire govt executive, my parents have sufficient mediclaim cover and I have to spend very less for their medical treatments. We wanted to buy a house in the metropolis and I had differences of opinion with her while selecting between a flat and a resale house. Meanwhile, my wife started sleeping in a separate room with my son, since last eight years. Our relationship was strained though I tried to keep everyone happy. My wife started removing a chunk of the money that I used to give her every month, in the name of saving. She started saying that she had saved all these money by her hardwork. I never knew that she was cutting all major food expenses and started to force my parents to live on dirty, rotten, un-cooked food. She even threatened my son and made him forget all good foods that he normally likes. Whenever, I tried to interfere by bring in some good food for my son or parents, she would immediately start uttering filthy and rowdy words to everyone, which were neither unheard of nor practiced by any of us in the family. My work sometimes calls for drinking with my office colleagues and that is highly un-acceptable to her. Of late she started forcing me to buy two separate flats, one for us and one for my parents. Even though I do not have a budget or means to afford two flats, still I somehow agreed. All because I wanted peace in the house at any cost. She started spying on my mobile to see with whom I am talking to, especially brokers who deal in properties. She started noting their numbers and calling them up separately, in my absence, and misleading them in proposing bad or litigated properties to me. When one of the brokers told me abt this, I charged my wife, why she should call up the said broker, without informing me. I also directed the broker not to listen to her and follow only my instructions. The broker was an idiot and when my wife called him up again, he confessed to my wife that I had asked him not to discuss abt these matters with my wife. My wife behaves madly when she gets irritated. She started charging me again and this time her language went worse. She even threatened to kill my parents, slowly and coolly, without harming them directly. Hope I have explained the situation I am currently in. Under such circumstances, what would be the best way to handle such a woman and keep my son and parents safe from her ? She is not at all interested to live with me as an obedient wife. She wont leave my house too, because she is only interested in my money. And for money, she can do any mad things and blame all of us. Keeping one's husband in a separate room for eight years is in itself a mental cruelty by the wife. On top of that, the black mailing she does for money and to fulfill her own interests, especially to keep my parents away or in a separate flat, is more cruel. She seldom even talks with my parents. My aged parents, who are mentally and physically now weak, has been forced to do all their daily works, all by themselves. I have just been able to get their daily clothes washed by the maid who works in our house. I am nearing 50 and this behavior of my wife hurts me very much.