Your setup is leaning towards tires with larger slip angle than what the nitto provide. That rear edge wear would indicate too much camber. The street miles should not affect the wear like that in such low use. You're also running high spring rates in the rear which is very unloaded and light, thereby reducing a lot of roll and decreasing traction on that axle. Everything combined, you need less camber there, or a higher slip angle tire (slick), dramatically soften dampening, or go back to the stock sway bar. With that much camber your front shouldn't be wearing like that. It's either being pushed into understeer from too fast entry, the spring rate or dampening are too soft, the bar is too small, or there's a front to rear balance issue.
If you're not ready for a true slick, maybe try another 100tw designed for greater slip angle like the nankang, maxxis, or toyo rr. I think you just need to bite the bullet and go R7. They can resist the heat this platform gives in the front end...