Grey-St, if you've lost your mind, I think you're in good company as many people are driven to distraction by trying to figure out the motivations and missing details of DM and/or MS's crimes, so you're not alone, IMO.
My frustration with many of the DM/MS associates is because I don't find them trustworthy and therefore I find it hard to sift through whatever they state as reliable and it is hard for me to feel confident that they are telling the truth - the whole truth. IMO it would have been far better had any of them offered up more information willingly about DM and/or MS but I always get the sense that they hold back in an effort to protect themselves and/or one or both accused.
When in contrast I think of
SL, LB's ex, he is a shining example of someone who risked a lot by opening himself (as an ex bf might be considered a prime suspect) to scrutiny by LE and yet despite that risk, SL pushed hard for TPS to investigate further LB's disappearance. SL IMO had a clear conscience whereas several of DM and/or MS's other associates were up to no good in one way or another IMO and would not likely want to deal with LE and endure LE's questions about their lives even in light of LB being missing, in possible peril, or worse.
As for whether or not LE in any jurisdiction have been or are currently investigating any other possible crimes related to DM and/or MS, I have no idea.
All MOO.