I know if you run the car for a while you will lose power and need another oil change. If you run the car a lot you will have to buy a new one as the loss of power can not be regained. That happened to me on the last GT mode race at High Speed Ring in the Ford GT.
As for the different displays of power, they are all differently displayed according to where you are viewing those numbers.
I have a question about the rigidity though. If you crash the car a number of times, do you need to get a refresher. I'm really asking if it has to do with crashing or just regular racing/driving. I would believe once it is available it should be used.
As tuning goes, the car is terrible in the rear end so I'm tuning it to keep the rear end in the rear. I'm trying to get the rear wheels planted on acceleration, while having the ability to keep the car straight under braking. It seems shifting the weight through springs and shocks helps. I used a bit of weight balance, but returned it to default, as it didn't help the car on braking. I'm not sure what I'm doing exactly, but the tuning guide did help me understand what I need to do.
EDIT: gtbadboy's times should be in the LUXY as
21.945
39.429