previous generations and silmarilion appearances are not well know among common folk, so yeah people mostly know about the movie versions, and want that, thus, it was transplanted into wow elves as well
no that much nowadays, if they had, Sylvanas would not be in a rush to find a way to get more, they suffered heavy losses in the war too.Forsaken have quite big population. To be honest, they could have bigger population than Horde in Kalimdor that consists of orcs and trolls that came on couple of ships.
Orcs came in big numbers, the wc3 campaign ships were not rly canon numbers, and later more came to orgrimmar