Yeah very thought provoking!!
Yeah I think that wasn't really him, it's the grief coming through when He heard all the people dying, which caused him to be angry because he wanted to change it, he was fed up with following the rules of time and getting hurt by them. Then when he did (or thought he had) what he did it brought an arogence out of him that was what he could have been (a bit like what the Master decided), but I think he was quickly brought back to earth by Brooks. He needed to learn the heard way to remember why he is like he is. The fact he was affected by what Brooks did means the Doctor's still there. Just a very hurt and fragile one.