Some annotations:

2.) I assign a lower probability to an extremely negative outcome because I believe it to be more likely that we will just die rather than survive and suffer. And in the case that someone only gets their AI partly right, I don't think it will be extremely negative. All in all, an extremely negative outcome seems rather unlikely. But negative (we're all dead), is already pretty negative.

4.) I believe that the SIAI currently only needs a little more support because they haven't said what they would do with a lot more support (money...) right now. I also believe we need a partly empirical approach, as suggested by Ben Goertzel, to learn more about the nature of intelligence.

5.) I don't have the education and time to research how likely other existential risks are, compared to risks from AI.