Good points, well made! I also think you're right on the sacking vs. the inquiry... we and he see the inquiry thing coming, especially when he comes back that second time and they bring up the photo, then by the third time, you see him defeated, despite that brilliant speech.
Come the next episode, you know there's no miracle cure for him, there are no more strings he can pull or puppets he can manipulate, like he did with Steve and Julius. Whereas when he is sacked, I think as an audience we have an idea it's coming, especially the look on Steve's face, and they've already reminded us that Malcolm orchestrated Steve's fall from grace before, so you have this awful idea that he is getting his revenge, but Malcolm, who is usually so suspicious of everyone, totally misses it.
He even sends Steve out to 'warm up' the press, without realising that has sealed his fate, as Steve then uses that time to announce Malcolm's resignation. Brilliantly played, but still so brutal. And he just seems vulnerable at so many points in that scene, like sitting down, that realisation, turning to see it on the TV... and then grasping for Nicola to save him!