Fascinating article! Among other things, I wasn't even aware of the twin categories for psychopathy, though I was vaguely aware of what one could call emotionally stable and unstable groups of psychopaths in relation to the personality traits they exhibit. Though it doesn't help that some of even very recent articles on the subject seem to lump the two into the same general category of "Psychopathy: lack of empathy and self-control, combined with impulsive behaviour", which does admittedly fit the secondary category. In the context of the "Dark Core" concept borrowed from the above article, primary psychopaths would probably have to be characterised by Machiavellianism and Moral disengagement.
Perhaps there's still some mixing and matching of negative traits going on in these definitions? It's that or I'm simply confused about some things.

I'm also very interested in the potential categorisation of psychopaths by structural dysmorphism of their brains:
We've been able to isolate separate negative personality traits and folks have been working on nailing down the structures that differentiate psychopaths specifically -- there are even recent breakthroughs in the field! Can we perhaps start putting together a model on that basis?

P.S. As for the abruptness of the final section, I hope that you will perhaps expand on the topic of EI-training in a future post. Still, I think ending it there was a good call -- certain length and partitioning considerations that improve digestibility are not without merit.