"95% of the population will starve to death" is very unlikely although I can't completely rule it out as a possibility. The research on nuclear winter is of a poor quality, and we should be funding better research.
"The world will regress to a pre-industrial-revolution lifestyle" seems to be a retreat from "civilization will end" (not that I agree with it).
>travel will be even more risky than in the Dark Ages thanks to fallout
The radioactive contamination caused by Chernobyl has persisted for decades. In contrast, the radionuclides created by nuclear explosions are of a very different nature and persist for weeks. 3 weeks after the end of the explosions, there will be no place except ground-zero craters (i.e., very small areas) where the levels of radioactivity remain at deadly levels. (But I definitely agree with you that during those critical 3 weeks, almost all people who decide to travel will end up dying unless they know a lot about nuclear war and have good radiation detectors.)
To repeat my overall point: the worst-case scenario for the outcome of AI research should be compared to an asteroid strike by an extremely large asteroid, not to nuclear war—because nuclear war is too tame in its effects to make a good comparison.
The reason I got involved in this discussion is that some people use the possibility of nuclear war as one reason for us to go forward with AI research as fast as possible. Such people argue that a sufficiently mature AI technology would eliminate the possibility of nuclear war. I think that is a fallacious argument become AI "progress" is the more potent of the two dangers.