You're right, it is interesting digging. But so far, race doesn't seem to be a significant part of the Doctrine of Discovery. It's absent from this:
'Associate Justice Joseph Story, a Unitarian, (1779-1845) later wrote: "As infidels, heathens, and savages, they [the Indians] were not allowed to possess the prerogatives belonging to absolute, sovereign and independent nations."'
Story's language is remarkably consistent with the divisions that were used as rationalizations for slavery before race became the prime rationalization.
I'll continue to ponder this. Thanks for pointing it out!