How much time I wait after knowing my wife is in affair with her school friend and collect proof

We are married since feb 2014 and having two kids. after marriage my wife started fights with me on small reasons and demand for the divorce but i ignored her and tried to save my marriage life by requesting because i am in dilemma of that she needs time to adjust with me and my family. after marriage my mother in law started demanding for child and by mutual consent we are agreed that no issue if we have first child early. after this incident she started demanding for stay in her mother's house for long periods and at the time of second child she stayed almost 1 year and 8 months at her house and same again me and my family request to her and her family to come to my home back and she agreed. Now from last two years she started finding ways to fight with me and my family members on any topic and started fighting with me when i am at home. started demanding for separate house and saying if i can't leave my mother and family then she will stay alone at new house and also giving me warnings that if you want to sleep with me do what I am saying and we are almost separated in same house from last 6 months. Now I got click in my mind that she has different intention to leave alone because she doesn't want to me as well for leaving separated life and when i ask what is problem with current joint house she has answer that i am not responsible for taking care of you and your mother. one more thing i noticed that she is using password apps and keep her phone and apps locked with passwords. whenever her phone not around her she started looking for it like phone is her life. Now want to know what is in phone that she is so curious and concerned about phone. I didn't get that my time to install spy software but i took WhatsApp access in my laptop that syncs her WhatsApp messages. Now i noticed that she is most active in WhatsApp in mid night 12 and chatting with her school friend. i started recording her WhatsApp chat and found that both are in affair and she wants to separated me and want to go with his lover. I have call statement, WhatsApp chat and Google location history she visited to her lover house. so i have proof of last 3 months only but i am sure both are in relationship from long time. So how much time i wait for filing divorce cas against her ? currently she is not aware about that now i know about her affair and we are not talking from last 3 months after she left my home. and i am continuing checking her activity chats savings for proof. please give me advice for time wait before filing ir i just tell her that now i know about you and don't want continue such life. i also want my child custody.