Sundering and specific character questions. [Spoilers]

[Vyrerus]

Atmosphere

Actually, the Moon let the Earth form an atmosphere to begin with. They shared their magnetospheres(the moon used to have one) for about 600 million years after the Moon formed. This let it deflect solar wind quite readily, as it was only 80,000 miles away from Earth back then (theoretically). In this way, it has given us our greatest boon, but it will also one day cause our rotation to slow to the point that our days match its revolutions, and so our days will be 648 hours long. Obviously that's some billions away, but... it'll get us before the Sun does.

completely unprotected.

By that logic, look up at the Sun in the day time sky. That's how much of the Earth it can protect >:B

A lot more goes into meteor impacts than you think. The Moon doesn't merely act as a physical shield, though I love to think of it as one, since it has many scars. When a meteor is drawn into the ecliptic, it is pulled by the Sun's gravity foremost, but it's affected by the Earth's and the Moon's as well. This can pull the meteor to them, but it may also unsteady its orbit and accelerate it towards the sun or away from Earth. But as a show, I think it's currently calculated that for every 43.3 meteoroid tons hit Earth, 1.4 hit the Moon. It is small, but not as small as you think.