As a child of abusive parent, I too found Harry's emotional state completely absurd. It was like the abuse was only physical, and so when the physical constraints were removed, viola! Harry is all better.

As a lover of fantasy, I found the Harry Potty world of magic to be absurd. The author just took ideas from many magic systems and just smashed them all together willy nilly. There was no reality in her magic system.

There is some fan conjecture that Harry Potty is a Horcrux.
And we know what the Diary/Horcrux did to Ginny in just one school year.
Imagine what Harry Potty, as a Horcrux would do to a very nice family, that he was forced upon for some 14 years.