The strange thing is that since you can't see the points in the Milky Way without a telescope, it's unclear why the Egyptians drew stars on the edge of their depiction of the Milky Way. It seems they would have assumed it's a long cloud or something like that. (Indeed, an old name for "galaxies" outside the Milky Way was "nebulae" until a few hundred years ago.)
> in Middle English also Milken-Way, Milk-white girdle, and Milky Cercle.
["Milken-Way" is a direct translation of the Latin name, and "Milky Cercle" is a direct translation of the Greek name. Girdle is less easy to explain.]
> The ancients speculated on what it was; some guessed it was a vast assemblage of stars (Democrates, Pythagoras, even Ovid)
I don't think there are any texts attributed to Pythagoras, but we might have a text that says he thought so, or that the Pythagoreans thought so.
(A) Inventing / discovering calculus in the 16th century is very impressive, doing the same in the 20th century much less so. (Indeed this has happened several times.)
(B) It would be a remarkable anticipation, which is similar.
Pedantically, all the stars you can see are in the Milky Way, but in the sense you mean, the furthest stars are the ones that form the fuzzy cloud but there are closer ones in the same plane that you can see, so it looks like a long cloud dotted with stars.
So you don't need to know the fuzzy bit is also stars to depict stars in it.
