I tend to agree a disconnect is more probable than a jam, but with fire in that area who knows? Possibly the section outboard of the fire had seized and the section inboard had sheared in such a way that remaining controls were still free. Or vice versa. To really confuse matters, the Convair was built at a time when the FAA, or designers, were going through a phase of favouring rudder/aileron interconnects. The CV- 580 had this, and what awful, heavy controls they were, too. If ever there was a contraption it was the 580.
The centred rudder in the video taken from outside the aircraft still suggests close to symmetric power - whether a lot or a little at the time is not so easy to deduce simply from estimating prop RPM. You'd need to know the manifold pressure and TAS to get a better idea.