Incorrect about the normal force. The peak normal force applied to the tire is a function of weight transfer only and does not change with a more flexible chassis. Total weight transfer is only a result of the geometry of the car (WB, track, roll centers) and the location of the mass relative to this geometry. The rate of weight transfer is influenced by all sorts of things like roll stiffness, damping and chassis compliance (which feeds into roll stiffness). The reason that chassis flex makes the car easier on its tires is because you are changing the F/R roll stiffness distribution as you roll and reducing the rate at which weight is transferred.