Tortional Stiffness?

As Colbert would say "easy peasy"

Yes but you will have to work-out the angle of rotation from examing displacement components. For small displacement theory, ds = R tiimes d(theta) so you could back-out d(theta) from that equation with ds = sqrt(dx^2 + dy^2). [assumes the rotation is in the XY plane). Get dx = UX and dy = UY from probing displacement components of a point on the structure at radius R. At least, that's how we've done it.