Hmm. I find it difficult to believe that he had an entity possess him for ten years. At least with the description he gives. I think too, this can teach fear to others, to get enchanted into such things. Ten years would be an awfully long time. He speaks about pleasurable energy, but also admits to having been going through some troubling core wound issues. If anything, what could've been holding him down, causing him to be stagnant, would be the healing of others with temporary 'good feeling' energy which could produce, not really a healing energy, but a dependency from they to him. This is easy a trap for other people. And then, the drain would certainly come. First he's going forth, healing or putting in the healing energy into stones for others to have, but then this sort of energy runs out, in some way. Keep doing that, and there's always going to be plenty to want more and more. Then the ego rush of being 'needed,' or perceived as a healer, when really an enabler who has charmed others via their dependencies. I think sure, entities can latch, but the core issue, IMO, was Kris himself, giving, others taking. The ego had created something it wanted to be, but it wasn't pure enough, for the right purposes, hence why he was stuck.
We cant be blaming everything on entities or ghosts or thoughtforms. They exist, but usually the biggest problem children are us.