Alimony & Divorce Filing

Respected Sir, I have been married for last 10 years and i have been facing challenges with getting space in my life from my spouse, at every point she has problem of me talking me to anyone, she thinks that to whom so ever girl / woman i talk for a long time, it means i am in relation with that girl / woman. I have never told her that she has to correct her self she should self understand that, now the situation has come up that i got frustrated of all this and i actually met a woman that understands me very well, i also have a good relation with her and mentally and physically satisfied with her as we both take care of each other very well. Because of this my current spouse came to know and has created a havoc in the family and is threatening me by sending lawyers notice and i came to a decision to end this marriage, apart from that i have a child of 5 years and 11 months and am ready to take the monetary responsibility of my child, my current spouse is educated but does not have any large earnings. I would like to know how can i fight for this and what is the amount of monthly alimony that should be paid for this, while i earn between 45,000/- to 50,000/- a month and she earns 7,000 to 8,000 in 3 months.