i'm not a farseer expert but i think i can give you some answer :
when you apply a force or an impulse using the ApplyLinearImpulse and ApplyForce method of the body object, you can specify a point to tell farseer where he has to apply the force/impulse on the targeted body.
To apply angular velocity you can use the ApplyAngularImpulse method of the body.
The Moment of inertia is a measure of an object's resistance to changes its rotation, in other word greater is this value harder it is to make it rotate.
Torque is like a force that rotate an object on an axis, it can be thought of as a twist.
You should watch the Sample code and play with it, it could be helpfull ;)