vstech, Thanks for the thoughts. Answers below.

[in the rear, there are metal dogbone links that connect the spindle to the subframe, did you rebuild or replace any of those? how do they look?

...All the metal links are fine. No deteration of the rubber. No axial movement between fasteners. With the disk hub removed and the metal links attached at the body, it is quite easy to move them around and check the condition of the rubber. But they are not cracked and have no movement along their length axis.

can you define "twitchy"? say, there is a lane with construction and as you cross the road grooves, the car tries to follow them?

...On a four lane road, with minimal variation from one lane to the other, when crossing the point where the two asphault patches meet, the car will have a slight side to side jerk.

or are you saying when the road pitches to the outside or on a curve the car tries to shift down the slope?

...No, it is actually very stable in curves

or is it all of a sudden the car just launches one way or the other with no reasoning behind it?

...no, not without reason. I can see the normal road variations, slight dips low spots that cause it to slightly jerk. None of my other vehicles respond in this manner, Chevy Truck, Honda Civic, Chevy Suburban, etc

50PSI on an automotive road tire? really? I'd start with fresh soft compound tires and see how it feels from there.

...understood, this was a test to see if increased tire pressure improved the condition (it did) or made it worse.