Bernie,
The Pedersoli Sharps is prone to broken firing pins.
For sure pull the hammer back to 1/2 cock prior to dropping the breech block lever. Reasons are two fold; with the hammer down all the way forward the firing pin is still protruding from the breech block, secondly by opening with the hammer down the firing pin drags across the brass and will for sure scar the head of the case.
More so the breech block when removed from the action will reveal the firing pin has probably managed to cause an outward dish around the circumference. This can be a result of dry firing or through normal use. That circumference protrusion will wreck havoc on the head of the cartridge case! After removing the firing pin from the breech block, use the nose of a flat punch to resurrect the flatness of the breech block face. Before you put all the parts back together try the firing pin fit through the resurrected hole and make sure it does not bind. If so use the appropriate size drill bit to clean up the firning pin hole.
Look at the rear of the firing pin and you will notice that the firing pin has a very small tit where the spindle lathe cut if from the rod stock. Good idea to dress the tit down flat. Also check the firing pin transfer bar where it mates with the firing pin, it to probably has a divit in the face. Might need dressing down with an Arkansas stone.....
Don't lose the small coil spring around the firing pin!
Lastly the question about firing pins breaking. Consider annealing the very point of the firing pin. Reasons why firing pins break, they are either binding or are too hard. For sure a soft firing pin won't snap like a piece of glass!
Hope this has been of some use........