It will fit. I've run 24,34, and 38MM offsets up front (all 20x8.5's) without any issues. My FRPP 18" factory chrome Bullitts spokes fit really close to the caliper but it clears.Does the bare wheel spin freely on the hub? What type/model of wheel did you purchase?
1/16th of an inch is enough. You can grind down the caliper of it really bothers you, but the suspension does not move in a way so that it will affect the ride of the car. Jack up one of the front tires, and spin the wheel by hand. If it doesn't rub there, then it won't rub while you are driving, either.
I am running 20x8.5 up front, too. I think the offset was 28mm, and 35mm for the rear 20x10's.