It's hard to say why the cause of death isn't listed on NamUs and DN but yes, PMP is a valuable site and very well-researched. And Scrambledeggs, your MP looks like a good possibility too, for the short height and possible ethnicity.
If I understand what I'm seeing correctly, the UID's teeth might be stained from smoking, unless that's just discoloration that happened post-mortem or from causes other than smoking (coffee/tea drinking) while he was still alive. And his teeth appear to be misaligned, which also appears to be the case in Kerstetter's third photo on Charley Project:
** WARNING: Post-mortem (skull only) photos at site below:**
https://identifyus.org/cases/7325
When I was a kid, Breezewood was always a stop on the drive to see our Pittsburgh-area relatives, and while it was such a fun place to get a burger, watch all the semis pull in and people-watch (so busy!) it's sad to think that all that time, this man was lying just off the road that we and others drove. I'd love to see him get his name back.
I at first thought that he could have been a postal carrier because of the clothes, but then he would have at least one patch on his shirt. I wonder if there are any other cases like Kerstetter's where a security guard disappeared, only with little or nothing of value missing from the company he worked for and thus the case received far less media attention.