Like most hubmotors these axles are not made of very good metal, though they're not as bad as some I've had. So you can strip the threads of the axle itself, but it's more likely you'll take out the nut first.
I don't know what torque is recommended for them, but I can crank the foot-long 1" box wrench down pretty seriously with the old Ezee v1 hubmotor's nuts I'm using on my MXUS v2 and v3 (one motor didn't come with any nuts, and the other had such soft ones they stripped out). I have a torque wrench and I should use that to check what torque they are actually at...but I haven't used it on these yet.
Regarding the torque at the wheel itself (not the nuts, but generated torque by the motor), try not to suddenly change directions on it (electric braking hard at high speed), as it is very hard on the axles and they may shear off at the shoulders.
Possible to fix on the non-wire side...not so easy on the wire side. :/
BTW, depending on what wind you have, there is some data on the MXUS threads indicating 250A phase currents might be saturating the motor (meaning lots of excess heat is being made for not significant extra torque).
I don't see any images; if you attach them directly to the post in the attachments tab, then anyone that sees the post can see the images.