your 335i has a lot more power than your old 330ci..that could factor into your DSC going nuts...there's just too much torque
in regards to "best winter tires," it's pretty much subjected to the preference of the drivers...some regard it as giving the best traction in the deep snow...some regard it as giving better responsiveness in the cold/snow... you should have done some more homework before you bought it...
To put you at ease, my m3 gets passed by corollas and civics daily ...who cares? Oh, I'm on 18" hankook w300..their reponsiveness is pretty crappy too, but it's expected ...If it bothers you a lot, go for high performance winter tires. I doubt it'll be any good for real snow, but since you don't seem to drive in those condition anyways, it might work for you.