The half cock notch is a safety feature of the 1911 but it is not a safety position, i.e. you should never carry the pistol loaded with the hammer on the half cock notch. This is probably the most dangerous way to carry a 1911. If the hammer is struck a sharp blow, say you drop the pistol and it lands on the hammer, the gun will probably fire as the half cock notch and sear nose are rather fragile. I remember one guy who died from a self inflicted gun shot wound like this.
The inertia firing pin should never be long enough to reach from the hammer at rest to the primer, if it does you need some serious work on that pistol.