The actual formula for moment (Which I call Torque) is given as $$\tau = \overrightarrow F \times \overrightarrow r.$$ where r is the position vector to the point where the force is applied from the axis of rotation. If the force is applied perpendicular to the axis, torque becomes length times force. 

To your first question, the answer is yes. The motor will stop. This is because the torque generated is enough to keep the motor at a constant angular velocity, opposing dissipative forces like friction. You need apply only a fraction of the motors net torque to stop it's rotation.

Your second question is relatively straightforward, and can be found easily on the internet. Nonetheless, I will answer it. Torque can be written as: $$\tau = I \alpha$$ where $\alpha$ is the angular acceleration. Both $\alpha$ and $I$. Are measured about an axis passing through the centrer of mass. Also, if $\omega$ is the angular velocity, $$\omega_{final} = \omega_{initial} + \alpha t$$. With that said, I'll leave plugging in the values and obtaining an answer to you.
(All anglular value use radian measure)