I don't think I would use a carbide decapping pin even if there was such a thing. Tool steel is a lot more forgiving. It will flex rather than shatter.
What I've done for undersized flash holes is turn the end of a hardened steel pin punch down to .060" diameter in a lathe and whenever I come across 'strange' brass, I punch a primer out of one with the modified pin punch and a hammer. I can then judge whether a standard decapping pin would fit down the flash hole. Since I made this, I haven't had to bug RCBS for any replacement pins because I haven't broken another one.
You can also put a decapping pin in an electric drill and touch up the diameter with sandpaper to make it a little smaller.
Tell your dad to loosen off the decapping rod in his die and rotate it while watching to see if it turns out of round. If it does, that WILL break the pin off the next time he tries to pop a primer.