Not replying to you specifically but want to weigh in on the pendant. My daughters all took jewelry making classes in a pre-college program and it looks so much like what they made. Simple, somewhat amateur-ish but by someone who had access to professional jewelry making equipment. All of which is to say that the symbol may be “I’m trying out these cool hammer strikes.” Look at the quality on Etsy - it looks much more “polished”. IMO. At the same time, it would be very identifiable to the artist so it might be a good idea for LE to try and deseminate it widely. Just thought. Also, I’m so impressed by the sleuthing on this thread! So many good searches and ideas!
ETA - also if LE are really interested in the “finder’s” role, I would get the DA together with finder’s attorney and give him immunity for any non-murder/sexual assault crimes unrelated to the body. Then it would be apparent if he was copper-stealing, drug using, etc. it would also incentivize him to explain why the repeated trips. Or not. Which would say something.