@Crim
You seem to forget he can also detect the "shadow" of any threat in the area. Even a hundred-blind poisoning attempt would leave his food covered in that shadow as a threat, which he could trace back to the origin.
The combination of the temple-style home and his previous "name" of Okakushi-sama makes me think that he was worshipped in one of those small, isolated villages that are often the settings of horror stories before he was moved to the facility. SCP indeed!
@Crim he decides what constitutes alive, and he can feel danger, so the moment you decide to put him to sleep, for easier killing, dead. Fire a missile to blow up around him, missile is a dud, and you are dead.
@Crim : I think you didnt get it, anything to do with the intention to harm him now or in 1000 years time is identified and will let him kill you before you can do it
Like the Vampirgurl in the last Chapter, not even her Plan worked in the End, even just randomly blowing up a whole Town without targeting him in particular will get you killed, because its a indirect try to kill him.