Don't worry, the moon can't fall out of orbit, it is going too fast around the Earth. It stays in orbit because the pull of the Earths' gravity balances the centrifugal force of its motion, like a ball on a string spun around your body. To slow the moon down would require a collision with a very very massive body in the solar system, and such a free moving body of that size does not exist or we would have seen it by now with our telescopes.

The Sun and Moon are hit by meteors all the time, so is the Earth. They have very little mass, so do not affect the orbits. The can cause craters, and that is what caused all the craters on the moon. However, most of the craters are billions of years old, when the solar system had many more rocks and asteroids flying around. Most of those are gone now, swept up by all the planets and the Sun.

John Vallerga