Legal Question in Family Law in Maryland

There are 2 kinds of custody--legal, which you now have jointly with the father, and residential or physical, which apparently you have alone. He is seeking shared residential custody, which is the same as "two party" custody, because he has learned that his support obligation is reduced if he has at least 35% of the overnights. The fact that he has generally ignored your efforts to get him to participate in the obligations of joint legal custody should be an argument against what he is trying to accomplish, along with the fact that judges generally don't like to disturb custody arrangements that seem to be working in the best interest of the child.