Another way of understanding G-d's limbs is as a functional definition. Although my foot looks nothing like the foot of the centipede or of a snail, the serve a very similar function - transportation. So also the metaphor of G-d's hand is in order to help us relate to a certain Function in the Realms Above. The reference to Kindness being G-d's right hand is from the Zohar, a section known to be said by Elijah the Prophet. In this paragraph in the Zohar, Elijah is connects the sephirot with various forces and functions of Creation and represents them allegorically as "limbs" of G-d's body:
They [the sephirot] are called ["limbs" of] a "body" relative to the "clothes" that cover over them. [These "limbs"] are arranged as follows: chesed (or loving-kindness) is the right arm, gevura (restraint) is the left arm, and tiferet (harmony) is the torso. Netzach (dominance) and hod (empathy) are the two legs, and yesod (foundation or channel) is the body's extremity, the sign of the Holy Covenant. Malchut (kingship) is the mouth. It is therefore called the "Oral Torah".
So just as the right hand represents a certain functional definition of one of the sephirot, each one of the limbs also represents a different function, a different way n which G-d interfaces with the creation. And since kabbala incorporates such physical images it is necessary to strip the images from their material form to understand the underlying message and spiritual form they are conveying.
