"To what limits would you go if you [and I will add the ones you love] are genuinely threatened?"
What purpose does such a question hold, I'd have to ask?
What I am personally capable of... and what I would rather DO in a threatening situation are two different things. Example:
In the news lately over in Odessa, TX, a man has been going around between 2am and 5am and robbing people at gun point in apartment parking lots. In almost every situation, a man was walking his wife/girlfriend out to her car on her way to work when confronted by this guy... who proceeds to rob them of their wallets and leaves. This guy is armed with a .22 rifle (go figure) but is threatening enough to get away with it. Should THIS happen to me and ONLY me, I'd probably just give him my wallet (as I'm broke most of the time) and count myself lucky. Now, should this ass try it with my WIFE... only God could save him from what I might do. I know what a .22 is capable of and I know what I am capable of. So long as my wife was out of the line of fire and I could keep the guys attention on me... I'd take the weapon from him no matter the cost. Period.
Foolish? Yup. I can take a lot from people, but I won't tolerate it when it effects loved ones. I just won't. Now, would I kill the guy? Not if I didn't have to and knowing aikido helps make that a possibility. But should push come to shove... yeah, I could. I wouldn't like it and I sure don't want to, but the answer is : yes, I am capable of it and could/would given the right circumstances.
But again... what good does it do to ask such a question? Until the moment comes to test your metal, you'll never really know exactlly what you will do and definitly not know the outcome of it.