As to your other questions, when I said electrical damping is almost always an order of magnitude greater than mechanical damping, what I am trying to say is the damping described as Qes is much greater than Qms, having a lower number. The mechanical damping is usually almost nil because the suspension is designed to move freely rather than to provide resistance to cone motion. That's what you want, actually. So all the damping you'll get is acoustic (from the loudspeaker cabinet) and electrical (from the woofer circuit, through the voice coil and amplifier output).

About the forces that cause bending of the cone at frequencies above the pistonic range, these are pure physics, related to mechanical stress/strain and resonance. The cone may be very strong, but as force is applied in the middle and the frequency rises, there comes a point where the cone itself goes into resonance. This is like the now famous Tacoma Narrows Bridge. In 1940 it bended and twisted enough to tear itself apart from aeroelastic flutter, a resonant vibration caused by forces from wind acting on the structure.

Thiele/Small parameters and the associated electromechanical parameters only describe the motion of the cone as a rigid piston, and they do not say anything about cone breakup. Cone flex behavior is determined by the cone material, shape and size and by the position where drive force is applied and where it is suspended by the spider and surround.