Re: causing no (serious) harm
When I read this thread, I am reminded of Saotome sensei discussing "satsu jin ken and katsu jin ken" the sword that gives life and the sword that kills. That must be in one of his books.
I am also reminded of a story I heard from Gleason sensei about some shihan who was being attacked in real life (outside of the dojo) by several people. The story goes that while dealing with the other attackers, the aikidoka noticed that one of the attackers who ended up flying past him headfirst at a brick wall - so that aikidoka somehow swotted at that flying attacker to change his direction so that the attacker hit the wall with his shoulder instead of his head. I think about this when I think about minimum damage.
Of course, ideally you want to do no damage. But since we are not ideal, we settle for doing the least amount. I think it is the same kind of idea as when people try to argue that there is no unselfish actions because it can be argued that the person performing the aaction does it selfishly for the good feeling - or whatever. The idea is that selfless actions and doing no harm are more spiritual goals to aspire to. IMO.