I have alot of sympathy for the situation you describe and want to help you if I can, if only by pointing you in the direction of those who might be better able to assist you.
If you do a Google search using the letters NANCM or that acronym you should find that the "National Assoication for Non-Custodial Mothers" website is brought up at the top of the list. You will need to register with them in order to access their forum, but once on there you will find much help and support (I think all the moderators or leaders of the forum will give you good advice or know where to get it). You will probably guess that such a forum or website will be totally committed to giving you as much help as possible and I hope you deserve it (you sound to me very much as though you do and your ex. and his family seems to be behaving pretty badly to my mind, though I haven't spoken to them obviously so shouldn't be too judgemental).
If my giving you this advice assists you as a parent I will be satisfied (assuming you are the good person I take you to be). I have already tried to contact one of the leading lights from the NANCM forum to tell them your story so you may find assistance arriving quicker then might otherwise be the case, as you do sound as though it could be very welcome at this time.
Good luck,
Graham