Family Law Questions? Ask a Family Lawyer Online.
Your in a tough situation - I've represented many people in similar situations.
You have little alternative but to file contempt motions if your up to it and the hearing. Possibly even a modification of the custody order; however, that get really expensive and time consuming if your up to that too. Document everything, itemize everything, date everything - you can't tape record though - and go to court. Take people with you to pick up the children so that they can testify to what happens at pick-up/drop-off times.
Ask that pick-ups/drop-offs occur at the police station so that you two don't have to come in contact.
I would also call your telephone company to see if you can get copies of the text messages - certainly don't erase them. You might even go to your DA's office with those text messages and see if they will charge her with harassment.
Good luck! Thanks for the question.