I’m sure they’ve done some of that, but it is very labor intensive to track down people that lived in an apartment building 40 years ago. LE resources are better used elsewhere. Besides, they know about the name and location he was using at that time. I’m suggesting a way to start filling in the blanks in the timeline, without draining the resources from LE.
Connecting with EVERY SINGLE LIVING MEMBER of those apartments should be a top priority, and the usage of said resources should be used to the maximum of their capabilities.
This is a very critical moment in the middle child's life. And no, it's not very labor intensive at all. I recall many of my neighbors from the apartments I lived in 30+ years ago. It's all about networking. It's very, very likely the middle childs mother was with Terry at this moment. Not maximizing every angle at this juncture would be poor police work.