To see if I understand; the front sprocket is the drive?
If so, can you change so the rear sprocket drives? Then the tension and compression on tracks would be in a better place
You could try something like this. Cut some thread into the remaining metal and then build up with this epoxy. Turn down until it takes the bearing
I’ve only tried once and not yet reassembled but the theory seems sound
Hi
You could remove the injectors and turn engine over either eh key while holding paper under the injectors to see if diesel is spraying out.
Hope that helps
Regards