Wife Expired and in laws filed a case after 6 months of her death, taken away my elder son

Marriage happened in the year 2012 - Inter caste, love & arranged marriage.My wife expired in the month of Oct - 21, due to blunt injury in abdomen - Went for bath, fallen down in the washroom - due to electrical geyser shock, as she was fallen on the stomach sleeping position the shower holder was under her. After 6 months in the month of April - 22, my in laws filed a case against me and my parents under Sections 302, 498A. My younger son is 43 days old when my wife was expired, on the date of funeral of my wife, they forcefully took my younger son and after sending me and my parents to remand in the month of April - 22 my in laws taken away my elder son also. My wife worked for a year, at that point of time, she used to go to office at 6.30 am and used to come back around 7 pm regularly, because of work stress and all, she used to take rest after reaching home. She did not spend time with me and my son. My mother and myself used to take care of all his home works etc., and unfortunately, I was in contact with another lady at that point of time in the year 19-20, by showing all those photos and chatting’s with her now my in laws filed a case against me and my parents. Now, for my elder son is around 9 years old and even while sending remand also he told whatever he saw when his mother was expired and he clearly told, there is no mistake of my father for her death. After taking him to their house, now they are misleading his immature mind and they are not allowing him to talk. Now, he also changed and sending voice messages to not to disturb his life.In view of the above, is it advisable to file a child custody petition for my elder son / for both the sons? - My father (64 yrs) and mother (57 yrs) stay along with me only since 2017. Now, how to proceed to prove my innocence in the court of law against 302 & against 498a, they were written that, they have given cash for my bike purchase - till date not having two wheeler and driving license also. Also mentioned that, they were given cash Rs. 2 lacs for flat purchase - I took a loan of Rs. 28 Lacs and also withdrawn the EPF amount and applied company loan and purchased. Not taken any money from them till date. Surprisingly the post-mortem report police received within 1 month only. We went around 5 to 6 times to police station to know the case status even. They did not answered anything and suddenly, they were saying, as the post-mortem report says, blunt injury in abdomen, they were not having any other option left to arrest me and my parents. My wife undergone cesarean section second time after around 9 years of gap, when she was expired on that day, she completed 42 days after cesarean operation. My father in law is around 60 yrs and mother in law is 55 yrs, my brother in law is also having 2 kids (son & daughter). I am a Govt Servant and if my kids stays along with me, they will get better education at my company school and free medical benefits also. Kindly review the above and suggest