Todd,
Just an observation, but it seems to me that you have spent a lot of time and effort patching the symptoms but you have not addressed the root cause. Here's what I suggest, loose the conventional axles and go with a NASCAR or SCORE Off-Road type floating hub. This will give you two taper bearings in place of the one you currently have and the axle no longer has to carry any weight it's only job is to transfer power. This company sells all the floating hub parts and kits you need to either convert an existing rear or a complete 9" floater housing.
http://9inchfloater.com/index.htm
Hope this helps!
Steve