A couple of thoughts on the FRJs.
I really like the new physics as it feels more 'real' (whatever that means when I've never driven anything like it!!) but it is a handful especially under brakes.
A few things I've found (which supports what others have said above):
* brake in a straight line as much as possible (which you are doing);
* use the minimal force on the pedal to get the car to slow down (and it's not much compared to, say, the GTs) and apply the brakes progressively (i.e. more as the car slows down rather than all at once);
* careful on the downshifts (perhaps a split second later than you might otherwise);
* stay on (but obviously reduce) the throttle while braking - well not always but it's especially helpful in faster corners to reduce oversteer;
* move the brake bias forward (e.g. the default set up at Slovakiaring is 51-49 but I find 54-46 or even 55-45 is better). You end up with cold rear brakes but that doesn't seem to matter (at least at my "pace").
The FRJs are also more tricky at some tracks than others - presumably partly due to the default set ups. For example I find the FRJs pretty stable at Zhuhai but a handful at Slovakiaring.
I am also slower on the new physics - as its harder. My best lap on the new physics at Slovakiaring is 5 seconds (!!!
!!!) slower [edit: now 4 - yay) than my old physics lap record. But I am enjoying the challenge a lot more so I'm okay with that.