The more I've thought about this, the more I've been wondering if the solution isn't dealing with the dogs at all. You and the owner have had lots of intermediaries filter the message for you, and him, in this situation. Perhaps you should sit down at a cafe over a cup of coffee and explain, in unquestionable words, what this dog situation is doing to your health and well-being. I know it's a long shot, but maybe, just maybe, the solution is direct communication between you two adults.

I figure this may be the answer since, while you've admitted to being armed, a good shot and, at least on the Internet, upset enough to warrant lethal force, you've waxed and waned on actually pulling the trigger. While I'm not against protecting yourself, I get the impression you don't want the drama, baggage and mental anguish involved with killing something without every option being exhausted.