Absolutely agree that the diagram omits lots of good parts from your post!
Is “do big damage” above or below human level? It probably depends on some unspecified assumptions, like whether we include groups of humans or just individuals...; anyway, the difficulty can’t be much higher, since we have examples like nuclear weapon states that reach it. It can’t be much lower, either, since it is lower-bounded by the ability of “callously-power-seeking humans”. Somewhere in that range.
What I like about the diagram:
It visualizes the dangerous zone between “do big damage” and “prevent big damage”. If this zone indeed exists, some levels of power are risky no matter what.
It highlights broad classes of approaches: those that prevent the “AGI” arrow from entering the danger zone (by limiting the power of AGI, making AGI corrigible, attempting pivotal acts, …) and those that make the danger zone more narrow (making society more resilient, improving defense, nanobots against gray goo?). Of course, that is a gross simplification and is not intended to dismiss the other insights in your post.
How does urine testing for iron deficiency work? I was under the impression that one needs to measure blood ferritin levels to get a meaningful result… but I might be wrong?