A. The ABILITY to inflict serious bodily injury. He is armed or reasonably appears to be armed.
Or not. We just buried a LEO yesterday who was trying to deal with a naked, paranoid crack addict. The latter got hold of the former's service piece and put 11 bullets into his head.
It differs from state to state, and I'd strongly advise those who carry concealed to be intimately familiar with their state's (and city's, if pertinent) laws concerning deadly force, and current on changes made to those laws. In my state (Washington) you are justified in using deadly force to prevent death or "grave physical injury" to yourself or to another. In Texas you may do so under some circumstances involving protection of property. The penalty for not knowing this is potentially a life term in prison.
Your statement is TRUE. In some states you can protect property.
The 5 rules will work in any state. It has a very good chance of working in even the most liberal state with no CCW carry law. If I am attacked in New York, Kalifornia, Illinois, and he has a weapon, I will still take my chances by following these rules with the law of any state.