He's very angry and planning on divorcing her when he gets out. He's got his temper in check and is already mentally reimagining his plan of action when free. He's a logical organized and honest person but realizes he must measure every word. Ranting will achieve negative results. He believes in his own world view and now realizes he can't trust his wife to respect that. He's seemingly calm because he already has a flexible plan that will be carried out as sure as thunder follows lightning.