You need to file for divorce to protect your property rights. While we do have common law marriage in Texas, there is no such thing as common law divorce. You must file a petition for divorce in the county where you live just like people married in a traditional ceremony. Good luck!
I would contact the attorney who signed off on the protective order and meet with that person about what you can do to have to order rescinded. You may not get anywhere and have to wait it out. Be cautious that you aren't being manipulated by the other party to get these charges dropped.
You may be entitled to an offset given the amount of time you've had the child, but you certainly cannot simply on your own decide to not pay child support. You need an experienced family law attorney to make this case for you and pursue a modification of the current order.