Wife cheating

My wife is cheating on me!! i know coz i have read their msgs on whats app etc.... they send photographs to each other, some times even nudes ( the face are not shown, but i know my its his coz it was from his phone number), i dont know the guy, he is from other state, my wife's native home-town, they only interact, call, msg, behind my back,everyday... and usually meet when my wife goes to visit my in-laws. everyday and mostly she deletes all the messages and pics from her phone.... but i stumbled upon a few when her phone was broken and copied it with my self......(non of the photographs are together, all single pics sent & recd) . i also spoke to her once back but she denied everything, and had a fight that i being immature.... i didnot have any proof or pics at that time so i kept silience.....and have never discussed or initiated the topic again!!! whenever they dress for a party, or buy new dress they exchange pics, which are immediately deleted after commenting ..... i have a few of them which i copied when ihad a chance.I also have a few of their chat conversation,( in which both confess to love)which i copied from her phone, the guy is from a well to do affluent family and also married!!! now the problem is i am going through the worst financial crisis of my life, and we do fight everyday over very pity things, for which i get blammed, she's has a very foul mouth, and also does get voilent.... we have'nt had a physical relation since last couple of years, because she didnt want too, ........ i have a very young child, whom i love the most, whenever we fight she always says that she'll leave with the son, and never let me see his face again....and i cant live without my child. sometimes i feel it is that guy who is instigating my wife againt me!!! kindly advice what do i do??? i m tired of all the fighting and this problem i m going through a mental torture,first financial complication and this my wife having affair!!! and what legal action can be taken against the guy? coz if my family breaks i dont want let him go scout free?? and how do i get my child custody...... can i take action against the guy u/s 497? please advice me on how to go about the whole thing!!!!