Before you pulled the diff apart did the wheels actually turn / spin ok ?
Easiest way before you pulled it all apart would have been to see if the car rolled freely out of gear on flat ground, Pushing it & also rolling down the road,
The axle bearings dont sound to good, & need to be changed but if they spin freely will not be the cause of the issue ...
How are the front wheels, do they spin ok ? just jack up the car & spin them ...
The orange sparks need to be tracked down but could be something scraping under the car ?
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