You should hire a qualified child custody attorney to help you with this as soon as possible. You need to file an original suit affecting the parent child relationship in order to get your conservatorship, possession, access and support rights fixed by a court of law. Once the child has resided in another state for six months, Texas will lose jurisdiction as the child's home state and you will be fighting this battle in Pennsylvania.
You should hire an attorney immediately to protect your daughter's heath safety and welfare and your rights to possession and access. If you are not married your attorney should file what's known as a Suit Affecting the Parent-Child relationship, Temporary Restraining Order and Request for Temporary Orders and have your baby's mother served.
If he has just recently been picked up, the court should bring him to a hearing and appoint an attorney for him. He needs to come up with some money quick to get out although often the AG will agree to let people out without having to pay the full amount.
The Attorney General for the state of Texas is one of the most efficient child support collectors in the country, but the reality is, the good people who work for them are overworked. So your best bet here is if you think you are getting weak representation is to hire your own private attorney.
I agree with Mr. Moore. It may be possible to extend the child support past the disabled child's 18th birthday but this needs to be reviewed by a qualified attorney. The facts you've provided give us more questions than answers.