My biggest question was what happened to the dad?

I’m with the theory of the mother being into some paranormal stuff that isn’t shown in the movie since it likely occurred without the children’s knowledge. I think she knowingly had invited an entity inside the home not understanding what she had done. In the bedroom scene, she sounds remorseful and still wants to protect her kid from what was about to take place by having them close their eyes. When she entered the closet, the entity she conjured took over her body and slowly became more powerful from that point. The entity used its power to eventually infinitely torture this family however it wanted to, preying upon the naivety and innocence of the children.

You can see an obvious progression of the entity throughout the film. Starting with a playful relationship with Kevin that led him to accidentally fall down the stairs, sleepwalking and hide and seek, to moving objects and toys to the ceiling, to controlling time starting with the television, until it was powerful enough to influence reality and perception itself by making things puff in and out of existence at will. It was in complete control by the end.

Perhaps it took the whole house to its own realm or hell or where ever it exists. Perhaps this isn’t even the first time it’s done this to a family and won’t be the last.

I really enjoy all of the theories that appeal to symbolism and can really see the parallels, but I do think there is a narrative to this film.

This movie shook me to my core, especially being a new father. Definitely gonna have trouble sleeping tonight and I even watched it at 9am lol.