This is the main reason I don't frequently eat chocolate anymore. Dark chocolate is both the tastiest and lowest-sugar chocolate, but its cacao-intensity increases your intake of metals.
If I recall correctly, however, the origin of the cacao makes some difference. Cacao from West Africa and Asia has a lot less lead and cadmium than from South America. Still, I think little chocolate, wherever it's from, is metal-free.
Related: I completely avoid any broth or stock made from chicken bones because it has way too much lead for me.
I claim to be able to feel the effects of the lead in the hours after I eat a meal containing chicken stock. I don't doubt your report about lead in chocolate, but I didn't feel the characteristic signs of my getting too much lead the last time I ate chocolate.
If I recall correctly, however, the origin of the cacao makes some difference. Cacao from West Africa and Asia has a lot less lead and cadmium than from South America. Still, I think little chocolate, wherever it's from, is metal-free.