well i doubt he's transforming into anything because magick cannot alter DNA, i would ask him about it.
adding blood to food is more unsanitary, but it could be used in a spell, as with the hair. these two sound like some type of binding, but i still say confront him about it.
the circle and hole in the plywood i don't know. while many pagans cast circles, it's not evil, and it's normally not drawn around a hole in the wall. screams could be several things, tv, neighbours, imagination, hard to say really. but i would talk to him about it, if he doesn't give sufficient answers, i would leave [mostly because sneaking blood into your food.] but it could just be a misunderstanding, so try and have a rational conversation.