Yes, the Blizzard downloader application will resume your download. Just open it and let it go.
Yes, Blizzard offers the full client from their website for free, only creating the account costs money.
Yes, Blizzard will keep your character if you cancel your account, should you decide to come back later (I don't know what the time limit is on this).
Yes, some people find WoW really boring. This is irrelevant to those of us who don't. 🙂