...I have had a similar experience to yours with my Granite BLX. I haven't broken as much as you have, but I have had to replace the transmission and It just seems like these 2WD BLX models don't have the sufficient strength to handle the power that the BLX system puts out.
I'm guessing it was done to lower the price? The 1/10 scale BLX models used to be $350 before 2016.
Do your self a favor and get yourself a sc10 diff. No more diff issues
Sucks about the plastic. My old furys are pretty bullet proof