Are the expenditures he has agreed to cover part of the divorce agreement?
I'd probably send him a very "business" email regarding payments of his child support including what will happen if he refuses to pay for the next 6 weeks, and I would give him 7 days to cough it up before filing contempt. As for the other things he has agreed to pay.....once you set a precedent of allowing him to dictate when he will and won't pay child support you have lost the war. it will never stop. While you may lose some things he promised to pay in the long run you will be better off tightening the noose and letting him know who is boss....the Courts are the boss.
Perhaps it would also be good to empower your son that he does not have to discuss anything about your life with your Ex.