I liked most of this post but you made a mistake....
A car will not UNDERsteer with a rear sway bar only. It will OVERsteer.
UNDERsteer is a condition where the front of the car wants to lose traction and run wide on turns instead of gripping and turning as desired.
OVERsteer is where the rear of the car feels loose and wants to spin the car out in turns.
Simple rule: The end of the car with the firmest spring and sway bar will lose traction first.