(I don't have answers to your specific questions, but here are some thoughts about the general problem.)

I agree with most of you said. I also assign significant probability mass to most parts of the argument for hope (but haven't thought about this enough to put numbers on this), though I too am not comforted on these parts because I also assign non-small chance to them going wrong. E.g., I have hope for "if AI is visible [and, I add, AI risk is understood] then authorities/elites will be taking safety measures".

That said, there are some steps in the argument for hope that I'm really worried about:

• I worry that even smart (Nobel prize-type) people may end up getting the problem completely wrong, because MIRI's argument tends to conspicuously not be reinvented independently elsewhere (even though I find myself agreeing with all of its major steps).
• I worry that even if they get it right, by the time we have visible signs of AGI we will be even closer to it than we are now, so there will be even less time to do the necessary basic research necessary to solve the problem, making it even less likely that it can be done in time.

Although it's also true that I assign some probability to e.g. AGI without visible signs, I think the above is currently the largest part of why I feel MIRI work is important.