Well, the jury is in, and the accused is already swinging in the wind...
I'll post the film of removing the jack leg from the rig later; for now, we'll skip straight to the end.
In the shop, I heated the top bolt on the leg -- it weighs about 45 lbs -- used the impact wrench to extract the 6" long bolt.
After allowing the entire cylinder to drain, I manually pulled on the foot and out came the rod. About a foot or so... Then, it hung up. I pulled harder, and a huge gouge from what appears to be a bolt or pin came into view.
At that point, the operation is over, says Power Gear. A complete replacement is my only option.
I'm hoping that the hyperextension was coincidental: perhaps a piece of debris rode up and down during previous uses and only became a factor when the jack was pulled out in its entirety, That would explain the multiple scratches on the leg.
Nonetheless, I still recommend extending jacks as little as possible, wipe those rods clean and keep them lubricated every few days.