This movie, and this comes from a complete horror fanatic since the age of six, had the potential to be the best horror movie I’ve ever seen. The first hour of the movie is, except a few lackluster scares and/or character flaws, pure gold. Three things ruined it;

Too much nonsense near the end started ruining the very well-paced mood.
The ending with the children (children, unfortunately, often lack the ability to be scary - few exceptions, being the Babadook for instance).
Things you just mentioned.

However, I don’t know which scenes of the entitity you’re talking about removing, but the one where he’s in the pool and turns his head towards the camera should definitely be in.