You’re not kidding about Texas law... I went after my ex on several occasions because the kids were missing massive amounts of school. At one point, when interviewed by Social Services, my youngest son told them that he did not go to school “because he didn’t have any clean clothes to wear.” I tried in vain for several years to get custody of my kids because of the neglect of their education by my ex.
Don’t rely on social services. Most of those workers are divorced women that have an ax to grind with all men (because they still hate their ex) and so they generally help the mothers and condemn the fathers. I once had a male CPS worker that found my ex guilty of abuse. He was immediately reassigned and then later fired. Fortunately the ruling was still documented and valid. Unfortunately, CPS didn’t see a need to do anything about it.
The best thing to do it document everything. Video or audio record every conversation, visit, and meeting with your ex or anybody that deals with your kids (like CPS, teachers, etc). In TX, you don’t have to let them know that you are recording them and it can be used as evidence in court. Also, get them into counseling if possible. Contact Justice for Children in Houston. They might be able to provide resources or advice about getting custody.