Who are the dynamic and flat characters in Faulkner's "Barn Burning"?

Mr. Harris is a flat character in that he serves a function in the story –he has an historical grievance against the Snopes, but does not develop or change in any significant way.  He, like Major de Spain, provides background for the other characters to act. The dynamic characters include Sarty, because he changes  from allowing Ab to brutalize him through most of the story until the end, when he understands more clearly the difference between right and wrong and warns Major de Spain that Ab intends to burn another barn. Ab is the most complex character in the story. He seems, in ordinary parlance, plain crazy, a trait which manifests itself through his desire to dominate and destroy others and their possessions.  Critics often call this a ‘God-complex,” but what underlies it is a sense of lack and powerlessness for which he tries to compensate by, for example, burning down barns.