I would try wrapping the spool here with a piece of rubber or thick cloth, then using a pair of pliers to rotate the spool back and forth in small movements on its axis while pulling down. The camera should be gently but firmly secured in a vice or other strong support while you do this.
You could also try putting a strong piece of string through the spool's slot and pulling straight down.
Or, some way of putting pressure on these two points, like by opening a large pair of needlenose pliers on them (again, use rubber to not mar the camera):