Divorce wanted

Sir, i am a state government employee. My marriage took place in August, 2009 which is a love cum arranged marriage. that person has no job and used to live on my salary. In 2010 we got two male children(twins). After marriage, my husband and in laws used to torture me. But i bore the pain for children. after child birth, as i am an orphan, they started torturing me with words and actions. As i have to go to job after completion of maternity leave, i kept children at in law house and we are in another town with my husband. My husband used to torture me in many ways. He has an illegal contact and used to leave me home alone and go out not even telling me where he is going. He used to keep that girl in phone and used to scold me like anything and beat me while she hears. One day my husband came home drunk and bet me black and blue. i was frustrated with his actions and joined in ladies hostel in 2011 October for my survival. From then onwards i am sending money for children at about 5 thousand per month. I used to go to my in law house In 2013 my husband blackmailed me to take the two children and look after them by myself or he will come to my office and shout on me. Then i shifted to a flat and used to live alone. My colleague cum friend used to love me from before my marriage. I too loved him. He used to meet me daily in the flat and used to help me in office work and share my sorrows. I want to give divorce to my husband and marry my friend. My husband is now doing a job and is asking me to come home. But, i did not go because i cant live with him as he is so much cruel person and tortures me so much. My husband now came to know about my relation with my colleague and bet him and took signatures on promisary notes and blank cheques forcedly. He is blackmailing me to come and live with him or he will book my friend with all those material he has. Today morning onwards i am going to my husband house and living with him. But i want to marry my friend as he looks after me with lot of care and he did many sacrifices for me. He is an unmarried person and want to marry me and look after my children with care. Please suggest me any way to give divorce to my husband;;