There is more than one place in the menu where you can adjust AI strength and from some places, the adjustment is not save. It is like that, once you find where the adjustment is save, problem solved.
One of the many quirks in RF2.
From the tone of your post, you appear a little frustrated with this title. Hopefully you will get to a better place, as it also offers many great simulation features.
At this time, it seems that we need to take RF2 for what it is as development is on hold and probably will stay that way.
It is not for the faint of hart.
RF2 is garbage,sorry.
It used to work a few years ago but now nothing but issues.
I have my GT3 fix with ACC.
NR2003 for Stock Cars.
AMS1 which is the best sim of them all,rock solid.
Raceroom for the SOUND.
RBR for rally.
AC for F1 and awesome modded everything.
RF2 for broken Auto Rotation,Broken sound on alot of the cars.