what should we do about being sued by the Department of Revenue for child support

Dept of Revenue (DOR) support cases do not deal with visitation or custody issues. These type of cases can only address child support related issues.  If your fiance was paying child support, it was the result of a court order.  If the DOR is now pursing him, most likely it is for back child support.  When it comes to a child support order, either you paid the support or you didn't.  If you cannot afford the ordered support amount, then you must file a supplemental petition for modification and ask the court to modify your support.  No modifications can be made until a court rules on a petition for modification, and any changes cannot be retroactive any farther back than the date the petition for modification is filed. If he wants visitation, he will have to file a petition for visitation against the mother directly and litigate that in family court, DOR lacks jurisdiction to deal with visitation or custody issues.