Fridge Brilliance: In The Tribe, Chris & Nicole's aunt doesn't give them many rules, but tells them she'll kick them out if all they do is party, flipping out at them at the end of the film because she thinks that's what they have been doing. The first impression is that she's unreasonably strict (Chris over 18, and Nicole's guardian), but the police station has a wall literally covered in missing person posters, most of them the age of Chris & Nicole. She's not being strict, she's fully aware that in the town, a lot of teenagers have gone to parties but never returned home.
When David is purposefully sucker punching Michael before their fight. He's deliberately trying to piss him off so he can trigger his bloodlust.
Fridge Logic: When Sam forces a mirror into Max's face when trying to figure out if he's a vampire, he has a reflection.
It's possible that inviting him in made the family unable to detect any of the signs, as part of "rendering you powerless."
Then why doesn't Nanook detect him as a vampire before hand, when the dog first meets with Max?
It renders the house powerless. including its pets.