I think it's very telling that he said "I'm harvesting" because it shows that deep down he is aware of the things that his commenters and people on threads like these often keep telling him about. That everyone around him, family and "friends", are taking advantage of him. That the institutions are doing everything they can to not help him. That any employers he might have can and will lowbrow him into legal, but indentured servitude. In one word, that he's being harvested. Deep into his subconscious he knows it, I am assure. The psychotropics only served to help bring that back up more easily.
Now that he is aware, he can do some introspection without the fear of being hurt, because, how can anyone get hurt if they can't feel pain anyways? If they are completely and utterly numb and broken already? So he admits this relationship he has with the world. And then, in an ironic but not entirely out-of-character change of heart, he actually takes action, not just reacts, and decides to go against the man who threatened him. He says "I'm harvesting" because he is, in turn, tired of being only at one side of that dynamic and now he feels indebted to some of that emotional energy, the energy of the victim that gets transponded to the victimiarium in every crime, which is sublime, in the Victorian sense of the word, for the same reason that horror films or combat sports are.
Which is to say, I think that DBDR is becoming wicked, unbridled. He's going through an intense, deep-rooted morphological reacomodation, I fear. Another piece of evidence for this is that he flat out told his mother that the next time he hears about her, it better be from a funeral director, lest he won't answer.
If, and that's a big supposition, he surives this ordeal at the sanatorium. He will come out a completely different man. One who is aware that he has nothing left to live for. One who has no doubts as to what he is anymore. One who has drunk the poison and become acquainted with its flavor. He claims to be laying in bed, all day, no doubt since he's physically extremely weakened, but the body demands movement, and if the corpse can't provide it, it flows into the mind, and the mind has no bounds, it can keep processing forever and ever. With no real obligations nor duties, he has no interruptions. Who is to say that he's not become a mad scientist with his laboratoray being his own psyche? A maddog who has rationality to his own madness is something to behold.
All it takes is one bad day for the sanest man to be reduced to lunacy. Now imagine seventy.