Rear end advice for racing with a 4 speed

Looking at your damaged axle pictures , I think your making this too complicated. Having experienced this exact axle failure/ side gear damage it appears the axle is not completely in the side gear. This is usually due to a low gear ratio /higher number. The fix is a ring gear spacer moving the carrier toward the smaller pinion gear. Learned this the hard way in a Super Stock 4 speed Dodge Charger.