Anytime you change all four tires, it's always a good idea to get a 4 wheel alignment done, not just balancing. That explains why the steering wheel is pulling. If you don't do an alignment, the tire's will probably wear unevenly.
And ofcoarse the ride has become harder. Bigger rims means less sidewall (rubber) on the tires. It has nothing to do with the brand or model of tire you have. Since the tire's are low profile, they don't take road impacts like what bigger meaty tires would like when you had the 18" wheels.
I can already see you getting rid of these wheels in a couple of weeks like the intake and fog lights haha =] =]