1. It is really unfortunate what you have gone through. However, committing suicide is not the answer to any problem.
2, You have said that your wife had an extra marital relationship with her brother-in-law. Do you have any proof of this? If yes, what is the nature of proof in your possession? Depending on the answers to these two questions you can file for divorce against your wife after a year has elapsed from the date of marriage.
3. In addition to filing for divorce, you can also prosecute your wife's brother-in-law for adultery.
4. A wife who commits infidelity has no right to seek alimony from her husband. Do not accede to her demand of paying Rs.5 lakhs to close the case and equivalent amount for mutual divorce. If you have proof of her infidelity then her claim to alimony will be rejected by the court.
5. You may unilaterally apply for divorce on the ground of adultery, as suggested earlier, which your wife can contest. Contested divorce cases run longer than mutual divorce, but if you have valid proof in your possession then you will be vindicated in the court.
6. Contest fittingly the false cases filed by your wife.