I wonder if he ever had the conversation with his parents about his future-I suspect not. Of course blaming Sheila was central to his plan which he put into operation from the moment the Police arrived.
Steve, we'll never know, but given that he looked up to Nevill, I imagine that for the most part, he went along with things which pleased him without losing too much of himself. To address the second part of your post I would have to accept that Julie isn't a liar.