Another question I have is "Can I safely unscrew the breech plug from the rifle and unload it, or do I have to shoot it?"
Unless I missed something, what is your M/L? It all depends on what you have. Some in-lines may or may not have removable breech plugs. Side-cockers do not or I should say, don't go there. NO, You don't have to shoot it, in order to remove the load. Perhaps the easies, is to use one of those CO2 discharger or then pull with a worm-jag and good range-rod. Don't use a wooden rod. again, all depends on what your are working with. ....
Be Safe !!!