Take the hub out. It is a machined cylinder in a machined bore (swing arm) and it should be impossible to have it anything but square. Regardless of your observation of the pinch area gap.
Take the pinch bolts out completely. Stick a wedge in (plastic or wood won't damage the swing arm) and spread that gap. Knock the hub out with a block of hard wood and a heavy hammer. (I had to do that the first time I serviced my rear hub)
It is not rocket science. Pretty basic stuff. The parts (other than the angular bearing) are pretty robust.
Hi Thank you, but of course the uneven gap surrounding the hub to swing arm makes it look as though it is not square. I don't know if the front face of the swing arm bore is out of square, are they cast?