It looks like you may have the collars reversed. The brake side one is about 32mm long, longer than it is wide. Yours looks about equal? The sprocket side one goes through the 9.5mm thick seal, about 15mm sticks past the bearing retainer. That makes it roughly 25mm total length.
The tire should be pretty much centered in the fork. I have a 100mm (2.4mm shy of 4 inches) and it isn't super close to anything. Mine is a 400, but I think the wheel etc. and rear fork are the same.