What Will Be The Correct Method Of Getting Divorce In This Case.

My brother married 8 years back, having 2 years of kid. Doesn't happy with her mariage because of understanding the issues and aggressive nature of his wife. They have been living in same house under a roof for name sake. My sister-in-law has no issue in living with him. Later on my brother met a girl who work with him to whom he likes and went out with her and stayed in a hotel together. Hotel bill caught by his wife and she took photo of dt bill and kept with her. Now sister-in-law's family threatening my brother saying they will humiliate him infront of his office and ensure he gets terminated frm job & ensure he go behind bars. We want to knw, 1. How can proceed wid strong ground 2. Possibility of divorce easily & time 3. Can they file falsecase & put our family and brother behind bars 4. How much alimony they can ask (my sister-in-law is doing job/earning) 5. Impact of hotel bill on case.6. Is it punishable, if he is not happy with his married life and want to settle in life with whom he loves.