Why would you assume that the metal that binds it with the greatest affinity isn't supposed to be there? It isn't uncommon that another atom can activate a protein, albeit poorly.

I did my own research, it is certainly essential. It's why moss has dissapeared, for example.

calmodulin is generally though to be regulated by changes in calcium levels.

Presumably in error.

biogenic lead bands were not apparent in the ~100-ka-old Belgian individual discussed above

No such data is shown, they measured a 5.4ka individual, in addition to the neanderthals.

decades of research have shown that there is no safe level for lead in humans and other animals

They got their indices the wrong way round. I don't deny there is a difference, I claim that the healthy state is with lead present.