You are right, I have to specify on which part the forces are working. The forces and the torque I mentioned are working on the belt. And the direction of the forces are are up or down as seen in your drawing fig 3 (so in a horizontal plane). At point 2 the belt is moving faster than the pulley so the pulley brakes the belt at point 2 by applying a force on the belt downward in the drawing. At point 1 the pulley moves faster than the belt and tries to accelerate the belt by applying a force on the belt upward in the drawing. These two forces at point 1 and 2 form a cw torque so at the underside of the drawing he belt is moved to the left of the drawing. Because the movement is upward in the drawing the belt is moving to the higher middle of the pulley.
"Here is another way to think of it. When you have slip the the tendency of the system will be to eliminate that slip, in this case that means matching the velocities of belt and pulley which is achieved by point 2 trying to move to the top of the crown."
But in a concave pulley the forces will not come to equilibrium. It constitutes an unstable system.