(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:
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.
One open question in AI risk strategy is: Can we trust the world's elite decision-makers (hereafter "elites") to navigate the creation of human-level AI (and beyond) just fine, without the kinds of special efforts that e.g. Bostrom and Yudkowsky think are needed?
Some reasons for concern include:
But if you were trying to argue for hope, you might argue along these lines (presented for the sake of argument; I don't actually endorse this argument):
The basic structure of this 'argument for hope' is due to Carl Shulman, though he doesn't necessarily endorse the details. (Also, it's just a rough argument, and as stated is not deductively valid.)
Personally, I am not very comforted by this argument because:
Obviously, there's a lot more for me to spell out here, and some of it may be unclear. The reason I'm posting these thoughts in such a rough state is so that MIRI can get some help on our research into this question.
In particular, I'd like to know: