7.5 & 8.5 are staggered.
245's can fit in the rear, but if you sit 3 guys in the back on a lowered car, it will rub the sidewall a little.
Yes, 8j's can take 225 or a 245. I would go with 225 all around, as u will be able to rotate the tires. Tire wear on the rears are usually not even, and it gets worst if your car has been lowered.
Best thing to do is to just go to a good tire guy and see what they say. I personally like the Michelin shop on old klang road.