He's so calm and collected about his behaviour which makes me even more angry with him.
ーHe's so calm and collected about his behaviour which makes me even more angry with him.
「彼は彼の行いに悪びれることがないので、私を余計ムカつかせる。」
calm and collected で平然と冷静な様子を表し、calm and collected about one's behaviour を使って「行いに平然、冷静としている=悪びれない」と表現できます。
makes me even more angry で「わたしをいっそう怒らせる」を使って「余計むかつかく」とも表現できます。
ご参考まで!