I've run Super Sports on both my 3500lb 69 Barracuda and my 2013 3700lb Mustang GT and to be honest, I think your tire wear isn't really abnormal. When you track a heavy car on a 300 treadware street tire, with an alignment that is remotely streetable, the outside of the tire is going to wear faster. I've found the pressure sweet spot for my SuperSports to be 38/34 on a road course, and 32/30 on a shorter autocross track. I have since switched to Falken RT615Ks and found the sidewalls to be stiffer than the Michelins, and that has improved the vagueness on turn-in you described. The new Dunlop Z2 will be the next tire I try, particularly since you can dismount them and run them on the other side of the car to equalize wear....