With his marriage fraying, Blake persuades his wife Charlotte to take a break from the city and visit his remote childhood home in rural Oregon. As they arrive at the farmhouse in the dead of night, they're attacked by an unseen animal and barricade themselves inside the home as the creature prowls the perimeter. But as the night stretches on, Blake begins to behave strangely, transforming into something unrecognizable.
It’s implied that Blake’s dad might’ve been at least emotionally abusive. We see him yelling at the boy early on, then Blake mentions how he left home as soon as he could. Mild.
The movie opens on a close up shot of ants attacking a wasp. The sound is loud and off-putting. There's no real reason or call back to this scene later, so it's a strange choice to open the film.
As others have mentioned, fingernails are shown gruesomely falling off and someone is shown with fingers missing. One not mentioned already is that someone grabs the blade of a knife and their hand is sliced. It's done in passing and not in close-up, but still worth mentioning.
Very much yes. More so than any werewolf movie I can think of. Writer/director Leigh Whannell said he drew inspiration from The Fly (1986), and the body horror influence is very prominent.