I think that's amazing too. He must have been able to imagine it in his head somehow. If not the precise details of the actual formalism, at least some intuitive sense for the kind of relationships they symbolize. Being forced to do that might arguably have aided his understanding.
True. The rather slow and cumbersome way he communicated by computer forced him to be pithy and prevented him from being too wordy.
Very true and everyone is saying that. But I suspect that he would prefer that everyone remember him not for his physical handicaps, but rather as a physicist and a man. There was a real human being trapped in that body.
That's probably a cultural thing. In the United States, in California at least, it's most common to refer to academics (at least formally) as "Dr. So-and-so". (Many of them think that's too formal and prefer to get on a first name basis as quickly as possible.) Calling them "Professor So-and-so" sounds faintly off, a little Germanic.