You need to obtain what is called an Agreed Order in Suit Affecting Parent-Child Relationship in order for any terms of possession and access to be enforceable by contempt with the court. Without a judge's signature on an order, you can not seek enforcement by the court.
You need to see an attorney as soon as possible to protect your interests in dividing the community estate. Although Texas is a "no fault" divorce state, the court can consider fault grounds in making the "just and right" division of the estate.
If you married the man in good faith, then you have what is called a putative marriage. Although Texas law treats the marriage as void in this circumstance, the law protects the innocent spouse by making the marriage putative. The legal effects of a putative marriage give you (assuming you acted in good faith and did not know of the prior marriage) the rights of a lawful spouse in property acquired during the relationship. In other words, you have the same community property rights for the...
The terms of the decree control. Unless there has been a modification of the decree which the court has given a ruling on, then the original terms still apply. Without a court order allowing your ex-husband to relocate outside of Dallas county, you can seek to enforce the terms of the original decree by contempt. The agreement you provided is merely enforceable as a contract, which means that it is not enforceable by contempt.
If you qualify, you can try legal aid of Northwest Texas. Also, the Dallas Association of Young Lawyers regularly holds free clinics on Saturdays throughout the metroplex where you can simply walk in and have a lawyer look at your papers at no charge.