Sorry you never got a reply to this post, which I've only just spotted. Usually you could can on getting a reply from one of the very helpful people on this forum.
You're right, surrounded by the normal aorists the present εναριζοι does stand out. The difference will be aspectual. I suppose it's what the grammarians would call "conative"—have a go at killing him. The other contemplated actions are in his power to accomplish, but this one there might be some doubt about. Still, I would have rather expected the aorist myself.
My nostalgic greetings to Yorkshire, where I spent the formative years of my life, the first fifteen.