Pdilemma--so the dad isn't in a position to be a full-time parent. Fine. The mother is in a position to be a full-time parent. Fine. The support agreement reflects this. Again, fine.
Numbers--by your own admission, your son isn't an angel. An impartial judge and social worker evaluated the situation and found the mother to be the better guardian. It happens.
Like I said, custody cases are emotion-filled affairs. But stictly speaking, neither of you two are the principal parties involved. Stoking resentments on your parts does no good, and makes it much more difficult for the parents to work together in a productive way. I'm not trying to be harsh, but you both seem over-involved in these cases which should really remain just between the parents in question, and this over-involvement can only negatively affect the children. It's hard, but sometimes the best thing to do is to take a few steps back and let things alone.