Wow! This is a long interesting thread.
I’m just going to comment on the latter part of “doing no harm”.
In my opinion the doing of harm relates to intention. But purely the intention of harming someone outside of personal self-defense or preservation. As in assaulting or murdering an innocent person, defrauding them, slandering them...basically hurting the other for the sake of it or for your own benefit.
Any act of self defense and the intention of defending yourself would fall outside the realm of doing harm, since defending yourself or a loved one is a “natural” act that is in accord with nature. So having a .38 in your nightstand and training to use it is intentional to DO HARM, but since the intention is based in self-defense and that act is natural it would seem to be entirely just.