A very interesting and thought provoking post -- I especially like the Q & A format.

I want to quibble with one bit:

How can I tell there aren't enough people out there, instead of supposing that we haven't yet figured out how to find and recruit them?

Basically, because it seems to me that if people had really huge amounts of epistemic rationality + competence + caring, they would already be impacting these problems. Their huge amounts of epistemic rationality and competence would allow them to find a path to high impact; and their caring would compel them to do it.

There is an empirical claim about the world that is implicit in that statement, and it is this claim I want to disagree with. Namely: I think having a high impact on the world is really, really hard. I would suggest it requires more than just rationality + competence + caring; for one thing, it requires a little bit of luck.

It also requires a good ability to persuade others who are not thinking rationally. Many such people respond to unreasonable confidence, emotional appeals, salesmanship, and other rhetorical tricks which may be more difficult to produce the more you are used to thinking things through rationally.