Explain the ending
The whole point of the villain "haunting" the house is that it belonged to him, that the father of the family wrongfully took it from him. He also has clear ties to the place, with his kids dying in the pool. This detail was the fundamental characteristic of his character.
Now at the end, however, he suddenly goes to the house next door. Why? He has no connections to this house at all. It never belonged to him. His kids didn't die here. For what reason should he haunt this place?