Looking at your setup, it seems like you have a really thick rear swaybar compared to what you have at the front
Looking at the Whiteline s13 swaybar sizes:
They have 27mm front and 22/24mm rear
Currently you are running 26mm (softest) front and 25mm rear
Generally on the s-chassis, you would want to set the front to full hard (for swaybar) and tune the rear to suit
In regards to the lower control arm, as long as you have it parallel to the ground, it will be sufficient and roll center do not suffer
I run -2.5 front, 7 degree castor and -2 rear 1mm toe in if that helps
Plenty of grip however i also run 245/255 tyre size