How to calculate maintenace in case of divorce

I was married in December 2020, my wife has extra marritial affair and i have whatsapp chat of her in proof. She is pregnant now. In Bharosa cell, she asked for own maintenance as well as child maintenence to me. She is working as a teacher and earning 18K per month. And even they are not agree for mutual divorce, My family tried contacting their parents but they are not picking our calls. I was earning gross salary of 11lakhs per yr.. and home take is 72K Per month. I also have personal loan of 15 lakhs. Now my question is 1) Can i send legal notice to them for divorce, bcz their family was not answering our calls. plz suggest the better precoess to contact them. 2) If i was not able to prove adultery in court, then she is eligible for maintenance. and if yes then what amount she will get? 3) What maintenance i need to pay for child, and amount would be same for all years or it may differ by yrs to yrs. and till when i will pay it, i mean till 18 yrs of child?