To loosen, not to tighten. I've stopped using mine for breaking off because it rarely works. Good old two foot breaker bar with an extension tube on it.
And against the rear brake, not the gearbox... Ideally you need a fat friend to sit on the bike and hold the rear brake.
As I understand it, the issue was micro fracturing around the radii behind the disc flange as it leads into the bearing. The axles are unique to V4 SF and Pani, so possibly they've run the shaft a little thin to save weight??? I don't know for sure.
176Nm. It should have this cast into the rear wheel. Be careful of the workshop manuals you can get online, most state incorrectly 230Nm for the wheel side nut, but this is for 1098 as it has a larger diameter axle. Sprocket side nut is 156Nm. Both with Moly grease on thread, washer and underside of nut.