Divorce under adultery

My parents are married for about 30 yrs. Out of the wedlock of them 2 children were born, me and my sister. I am about 26 yrs old and my sister is about 21 yrs old, and our education is going on, and both of us are unmarried. My father was director of a central govt. medical college and recently retired from service and gets a pension of about 60000rs. My mother is class 12 pass. We have a house which is joint property of my father and mother. My mother is a housewife and until now is residing in the said house. My father built the house from his own income and taking loan from the bank(the loan has been paid in full). For last 10 yrs my mother has led her life in adultery with various persons of which me and my sister are eyewitness. My parents have no physical relation for past 10 yrs. But we all live in the said house. Me and my sister want to stay with my father if finally separation takes place. Recently my father has filed a divorce case under adultery,cruelty and desertion. After that my mother has filed a case for inter rim maintenance under section 24 of HMA, and requesting the court to pay her 26000rs per month and 60000rs one time for litigation expenses. My questions are- 1. What may be the approx amount my father has to pay her as inter rim maintenance? 2. What is the approx amount of time to solve the whole matter? 3. After the case is solved is there any chance that my father has to pay maintenance to her? 4. Is there any provision in law where major children can file a case against their adulterious mother on ground of cruelty?