Mike:
Based upon the logistical reality of your location I think you did the best that could have been done, short of simply calling LE and hiding until they showed up. The problem with that scenario is that, in rural areas such as ours it could well be half an hour or more before someone was able to reach your home, especially in a low-priority call like a stranded motorist. In that time, what is the guy outside doing? Is he really a stranded motorist, or is he moving everything that isn't nailed down from your machine shed to a truck that was parked somewhere outside your field of vision? Or worse, is he scouting around your house, trying to find the easiest way to get inside to turn you and Audrey into statistics? We do not live in a perfect world, and based upon my experience, I believe that you made the best imperfect decision available in an imperfect situation.
The physical changes you describe are something with which I am familiar. In my former LE career I have been forced to look at somebody over a gun sight on more than one occasion, and to even introduce the booger hook to Mr. Bang Switch on one occasion. In that instance I waited a fraction of a second longer than I should have. All I can say is thank God for kevlar. And I can assure you that, God forbid, should another situation arise, that hesitation will NOT occur again.