RE: How many pellets in the head/neck area
A target I used a while back, (one that showed the spinal column and brain outlined), had printed in the lower conrner, "6 or more pellets in the vital area for a clean harvest".
Obviously one pellet in the brain is all you need, but having at least 6 in the spine / brain outline should mean that your pattern is concentrated enough at that particular distance to be ethical.