A Half-Angle Locus

In the coordinate plane, let $A(-1, 0)$, $B(1, 0)$, and $P(x_0, y_0)$, where triangle $PAB$ satisfies

1. Can $(0, -1)$ be the coordinates of $P$? 2. Prove that triangle $PAB$ is a right triangle. 3. Let $\Omega$ be the locus of $P$. A line $l$ through the point $(2, 1)$ meets $\Omega$, from left to right, at three points $M, N, Q$. If exactly one such line $l$ satisfies $|MQ| \cdot |NQ| = m$, find the range of possible values of $m$.