Hello,
1) No case of cheating will lie against your father in law as marriage is a result of consent of two adults.
2) Need to know under which sections of Hindu Marriage Act you have filed the case to advise you better.
3) Did you move a nullity petition or was it on grounds of adultery the petition was filed? What is the status of the case now?
4) If the wife is not employed she can file for maintenance.
5) Of you succeed in proving adultery or of the marriage is nullified you won't be liable to pay