1. Yes , slapping is considered to be domestic violence.
2.Anyway forget this case.First find out whether your wife still loves you or not. Give her more time,love and affection and try to wean her away from her ex-boy friend.
3. If you're successful then she will on her own would withdraw the case.
4. Otherwise if she is in love with her boyfriend then you better come out of this marriage. Offer to her to free her by way of mutual divorce whereby she will withdraw the case and both of you will be freed from each other.