Sorry, jumping in, but, oh what an interesting discussion! And I say it as a Wesley stan, I never really imagined seeing his character that way. To me, the way his character became more insulated in later seasons was also partially due to a sense of shame: of course, he felt wronged but he also felt obviously responsible for what happened to Connor and the rest of his makeshift family. He also felt unsure of his role, he was basically back to being an outsider, back at his starting point in season 1. Wesley always had a purpose, having been born and bred as a Watcher, but it was after he joined Angel's crew that he really came into his own and become able to fulfill that purpose. So, after the Connor accident he was also coping with a radical paradigm shift: who is he on his own and without Angel?
(Also, Wesley's relationship with Faith and Illyria are so fascinating to me!)

But then again I may be overly invested and reading too much stuff in the text... :D