How do I make predictions about the future to make sense of what to do with my life?

I know opinions about these kinds questions differ widely, and I think you shouldn't take too much advice from people who don't know anything about you. Regardless, I think the answers depend a lot on what set of options is or seems available to you.

For the first set of questions, do any of the options you'd consider seem likely to change the answer of "how many years?" If not, I would probably not use that as a deciding factor. You're building a life for yourself, it's unlikely the things you value only have value in the future and not the present, and there's enough probability that the answer is "at least decades" to make accounting for long timelines in your plans worthwhile.

For the second, this is harder and depends a lot on where you are, where you can easily go, where you have personal or family ties, how much money and other resources you have available, and how exposed you currently are to different kinds of economic and geopolitical changes.

As for personal anecdotes: none of the career options I considered had to do with AI, so I've treated the first set of questions as irrelevant to my own career path. I do understand that AI going well is extremely high-importance and high-variance, but I'm still focusing on the much lower-variance problem of climate change (and relatedly, energy, food, water, transportation, etc.). Sure, it won't make a difference if humanity goes extinct in 2035, but neither would any other path I took. I've also had the luxury of mostly being able to ignore the second set of questions, but FWIW I work fully remote and travel full time, which has the side effects of preserving optionality and of teaching me how to be transplantable and not get tied to hard-to-transport stuff.