Answer to Question 1
Kuiper belt
Answer to Question 2
Observing from Mars would give us a longer baseline in order to measure parallax angles. In addition, the blurring caused by Earth's atmosphere smears star images. Even when astronomers average together many observations, they cannot measure parallax from an Earth observatory with uncertainty greater than about 0.02 arc second from Earth. Measuring parallaxes from Marshabove the blurring effects of Earth's atmospherewould yield a more accurate estimation.