I have nothing polite to say about this situation and am trying real hard not to say something so incendiary it's ban-worthy. It sounds like this msn does not respect you or your time or work, on any issue, and is telling you that. If he wants custody he should try proving he can handle any amount of responsible interaction. I'd suggest taking notes and recording your attempts to get him following through. Tell him you are doing so but do not allow him any access to your records. This will be important for the court case. Perhaps email copies to your sister. If he is not afraid of court, take him to civil court and tell a jury he would rather pay a stranger to take care of his kids than support their mother. He is counting on you feeling too intimidated to follow through on any threats, but you know you deserve better than being used for free labor and deprived of your independence and being treated this way.