I would have gone with a rear offset in the region of 28
Remember, you not only went a half inch wider, but also used a lower offset than stock.. so basically pushed your wheels "out" by around 20mm
The rear negative camber is probably causing the wheels not to touch the fender (if that's the case), but as you go further down the wheel, it gets closer to the bumper and will touch.
Nothing much you can do to the bumper, except try cutting, but that's not ideal.
A few mm makes a huge difference when it comes to touching, which is why you need to know what you're buying to ensure you fit the correct offset and width wheels.