Webbshooter,
Howdy! Sorry I haven't jumped in here to reply, been a bit busy. To answer your first question, yes. John Wayne got the "Duke" moniquer from his dog. I have, somewhere , a vidieo with his biography on it and it mentions this.
As to your Post Script, I only have an opinion. Many self defence shootings probably weren't reported. In fact,accidental shootings being reported probably only happened in larger towns where someone might keep up with such stuff. I don't think a regular cowpoke on the range, or a prospector or mountain man made it a point to write down or tell the Authorities if he was forced to shoot a bandit or wild critter or defend against indians. He might brag in the saloon later, but that would be it. Also, I wonder about some of the "accidental" shootings. The "it just went off! I swear!" phrase is one of the oldest murder coverups of all times. Modern ballistics can disprove such claims today but in the old days this technology just didn't exist. Hope this helps!