Wait you said on post #9 that your WL is set to the lowest hole...then in post #11 you say it is 3rd from the top??
Overall the lower you move the propeller down, the more spring rate you need (your 200# should be fine and allow you to) and the more understeer.
"stiffening" rebound shock adjustment slows down the shocks ability to extend.
"softening" rebound shock adjustment allows the shock to extend quicker.
I have found there is no exact science to suspension tuning. There are obvious DO's and DON'Ts but it boils down to gaining seat time and growing with the car so you two mesh well together to shave seconds.
I have strano springs and koni rebound adj shocks...DON"T adjust rear shocks to full stiff or it will be as if your rear end is on ice....ask me how I know
It's all controlling the weight transfer rate and matching it to your driving style. If the rear is allowed to transfer the weight faster and therefore reach the grip limit of the tire faster than the front...oversteer. That comes from stiff rear shocks,stiff bars, stiff springs and more air in the rear tire.
You could get in my car and hate it. But it works well for me. Trial and error and have fun!
IMO, since you just got new C/O's, set everything to "neutral" or middle ground. Drive the car and tweak one thing at a time. Figure out what you want the car to do that it's not doing, and adjust accordingly.