What will be the correct method of divorce in this Case?

My Bro married 8 yrs back, hav 2 yrs kid. Doesn't happy with her mariage bcoz of understanding issues and aggressive nature of his wife. dy hv been living in same house under a roof for name sake. My sis in law hav no issue in living wid 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 sis in law family threatening my bro saying dy 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 dy file falsecase & put our family and brother behind bars 4.How mch alimony dy can ask (my sis 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.