I've never seen such extensive damage from a botched cut. A professional repair would probably cost more than it's worth. If it was cut for a large frame, it might be useable on a smaller frame. No way would I apply some epoxy just to the exterior and use it. It would need internal reinforcement too. As I've noted, it is possible to fill the entire damaged length with solid epoxy.

Next time, mark the cut line and wrap with masking tape below the line. Make short cuts around the perimeter, no more than half way through the first time around, then go around a second time to go through. A crooked cut can be fixed with a sanding block.