I don't know why they had to use Sandman as the main villian in this move. He has to be the most gay and unknown villian in the entire series. At least they could have done Hobgoblin, Harry's Green Goblin, or something else.
Also, I think I figured out something about the suit. From what I've read, in the comics Spidey dons an emo-black suit for a short while, right before he becomes infected by the alien. So perhaps he does get infected by the alien, but Venom doesn't show up until the end of the movie or something.