The motion, as far as being "to abate ongoing support," sounds like it means whoever is paying the support is trying to have it reduced.  Establishing arrears means settling exactly how much is owed, as of a particular date;  this will reduce that amount to a judgment, that can be enforced like any other judgment and in a few special ways as well.

If your husband is the one who's paying the support, or supposed to be, DOR is coming after him for not keeping up.