vampire mode is designed for stealth/illusion characters. That's it. If you aren't a stealther, vampirism isn't for you. Also Dark Elfs make the best vampires, check out my post over there.
the game is brand new man, you encountered a bug. there is no way that particular npc should attack you, but there it is. Have you updated to the 1.1 patch btw? You should if u havent, it fixes a lot of these bugs. I haven't encountered any btw.
Stealth/Illusion characters have no trouble finding someone sleeping to feed on. All you have to do, is go to some keep (skyrim is infested with bandit keeps)
That, or just go into a town all stealthed during the night and feed in some house. Really isn't hard at all lol!. You should know, being a werewolf is fun and there is no downside at all
http://www.gamesas.com/index.php?/topic/1272685-character-creation-help/page__view__findpost__p__19269091 (view this post for some benefits to being a vampire, and how to use them)
two ways I know of to cure once self of vampirism. First is that guy that needs a black soul gem and perferoms the ritual, speak to inkeepers to find out about him. Then there is the Companions quest line. it doesnt take too long before they turn you into a werewofl. that heals u of vampirism (its impossible to contract werewofl'sm any other way as a vampirism, as vamps are immune to deceases)