Doctor Wolf, apparently, had a great many problems. Regardless of whether he could have done otherwise at any step in the process, the fact remains that he did not resolve these problems, and they have now had an irreparable impact upon the lives of Wolf's wife and son - ruining her life and ending his. However Stephen is dealt with, whatever becomes of his life, the damage is done and cannot be undone.
Wolf's insistence that his son housed the Goddamned Devil is a symptom of other, deeper problems. What I'd like to focus on here is that there is a particular kind of crazy evident in his words: not seeing the Devil in his son per se, but seeing the Devil at all. The idea that there is a malicious, implacable, intelligent, and covert agency at work in the world, an eternal and irredeemable force for corruption. Where you see the Goddamned Devil doesn't matter; thinking that the Goddamned Devil is real is just plain nuts.
As I said, this is itself a symptom, the particular way that some deeper problem has manifested. But we can see the crazy in it, just the same. There's no getting to that conclusion without some manner of crazy being involved at some step of the process. Whether Dr. Wolf can ever be free of his problems remains to be seen - the murder of his son will doubtless cause additional complications - but my heart goes out to his wife, to him, and everyone who has been touched by this tragedy, regardless of their metaphysical convictions. This is just too much.