DALLAS — In the gymnasium, the anger and frustration were palpable. It was felt in the words of a pastor, who told the crowded auditorium he was tired of prayer not being backed by action. It came from the mouth of Congresswoman Eddie Bernice Johnson, who said children shouldn’t be afraid a gunman would come shoot them, and that leaders needed to understand that. And to Beto O’Rourke, the former representative from El Paso for whom the crowd gathered for that evening, the question came down to this: How can Texas protect its kids? He began to explore the answer Wednesday night as he begins the…