very nice analysis!
The Dallara bouncing like crazy is most probably a setup issue, with the teams wanting to run with certain settings that make the car nearly uncontrollable on the bumps.
The idea behind these settings is to control body heave motions "better", helping the aero side a bit. But it is arguable that this really helps, as the car doesn't jump anymore on its suspensions, but on its tyres making the movements uncontrollable.
On some tracks, these extreme settings could help in heating the tyres up, but i guess they really didn't need it in Portimao...