I have just defeated the Earth Temple in Skyward Sword. I have some questions on the story. May someone fill me in?

This is what I could all gather --

Skyloft was created by a 'Goddess' to protect the humans of the Surface from the dangers. The Goddess, with the help of other species, banished the dangers from the Surface. Centuries later, the Goddess's prophecy will be fulfilled. Zelda, a normal girl of Skyloft, was destined to be the Spirit Maiden, and Link, a normal boy of Skyloft, was destined to be the Chosen Hero of the Goddess. They are both to prevent/end the Apocalypse that is bound to happen on the Surface of earth. Zelda, however, was forcibly dragged down to the surface by the Demon Lord, Ghirahim. Link and Fi, the guide of the Goddess, set out to find Zelda. Along the way, Link learns that Zelda has to purify herself in the Skyview Spring and the Earth Spring. Link was only able to see her in the Earth Spring for a short while. An unknown woman (Agent of the Goddess) prevented the two from connecting. Zelda is then off to the Gate of Time.

QUESTIONS --

1. Do I have the story right so far?
2. Why was Zelda dragged down by the Tornado?
3. How did Ghirahim know about Zelda's destiny before hand?
4. Why does Zelda have to purify herself?
5. Why did that woman prevent Zelda from talking to Link?
6. How did the agent know of these destinies?
7. Aren't Zelda and Link suppose to work together?

ALSO ALSO ALSO

If any of these questions are to be answered in the remainder of the Story, please say so and DO NOT state the answer.