First and foremost, thank you for choosing justanswer.com. I am a licensed criminal defense attorney and member of the American Bar Association and I believe I can give you some guidance.
Your main question seems to be this: "Is there anything I can do before he is transported back to CO?"
Unfortunately, the answer is one you probably do not want to hear and that answer is "no". Your brother is on the arrest warrant detainer out of Colorado and, because of this, nothing can be done in Texas aside from fight extradition to Colorado. Fighting extradition would be a losing battle because Colorado seems to have had the right to issue the warrant and, unless there is a case of mistaken identity, extradition would be wholly legal.
Nothing can be done in Texas about the charges or the warrant because both the charges, and the warrant, precipitate from the state of Colorado. Hiring an attorney in Texas, at this juncture, would be futile and, potentially, a waste of a good amount of money if you hire an attorney who is willing to file frivilous motions.
I know this isn't the answer you were hoping for, but I hope you have found it helpful. Please, click "Accept" if you have found my answer helpful so I may be given credit for my response. Good luck to you and your brother!!!