Explain the significance of this sentence: "My nerves were in a state of constant tension, my face took on a stiff, noncommittal expression, beginning to look like Brother Jack's and the other leaders",

This reflects the narrator not knowing where he stands with the Brotherhood. He finds the tension stressful. Not knowing his standing is worse than knowing he is no longer valued. The narrator began to feel like the leaders of the Brotherhood look, "stiff" and "noncommittal".