1) contact a detective agency . gather all evidence of her adultery .
2) file criminal complaint of adultery against her lover . unfortunately your wife cannot be booked for adultery as law regards lady as victim
3) file for divorce on grounds of mental cruelty and adultery
4) stop paying monthly expenses to your wife since your wife is now claiming maintenance . based on court orders pay maintenance .
5) you have not mentioned whether your wife is working or not . if she is working she wont get maintenance but you will have to pay maintenance for your children .
6) come back to India obtain AB in 498A case and fight case on merits