Originally Posted by Otis

If the prongs are already broken, then saving it is a waste of time. Plus they are broken because that thing is really stuck on there. Unscrew the outer plate. Use a pin spanner if possible, but most likely a drift and hammer will be needed. It is reverse thread.

Once the plate is off you can pull off the cogset and let all the bearings roll onto your shop floor. Let this happen as it will make you feel better about ruining the rest of the freewheel body. Once all the cogs are off you should have a nice exposed snout you can firmly clamp in your bench vise. Clamp and turn the wheel counter-clockwise and it should come off. If not use a little heat and penetrating fluid until it does.