Ken,
The stock size 14" wheel is 5.5J/14 with +45 offset.
Yeah, your right about the offsets and that explains why you have some rubbing in the rear of your fit.
Some guys in Japan get wider rear tires to fit by bending and triming the sheetmetal where the rear bumper attaches.
Maybe this picture will help show the problem.
But this screw is the real problem that has to be dealt with if you want to have tires that fill out the wheel well or large sizes like 18"s.
D