Only dud moment for me was the Doctor's 'ouch' when Diana Rigg fell off the stairs. Didn't think the Doctor would make a joke out of someone's death and felt out of character. But it was only a minor quibble.
You're right, it is generally out of character, but I interpreted that as meaning that the Doctor was so unbelievably revolted by what Mrs. Gillyflower (Diana Rigg's character) had done, that he could not muster any sympathy at all. For the Doctor to just say "ouch" indicates the extent of his utter contempt.
Last part sounds, intentionally or not, a bit vengeful, which I don't think was the case, but the indifference yes.
The Doctor's always liked guns, pain and death.