I was a bit confused when I first read the chapter, but on a second look, it appears as though it was a bit intentional.
The reason why he keeps using "IT", is that he's a Demon, and views humanity as something low, kinda like animals. He doesn't use pronouns like 'he' or 'she'. I mean, why would you when you're a demon.
Though, there are still grammar issues despite that revelation.