So sorry to hear this Nick!
Get going with your lawyer, and make sure you have documented evidence of everything that you're going to "use" against her, otherwise it will be your word against hers.
Also, please remember that you're not using your son against his mother, you're fighting FOR your son. (Not saying that you're going to do that, just making a statement.) Your son's not going to know any better, so please don't paint the other parent in a bad light, so much as it may be true.
Lastly, I wish you peace and ability to get through this easily.