Thank you for giving me this POV, it has helped me to gain another perception of the characters and their motivations.
Your points on religion in Western world are very interesting because there has always been conflict between teachings and real, deep message it brings. Instead of deep meaning of repentance and redemption, generations have been scared by eternal suffering as paying for the sins on this world.
You have made me wonder my own believes, why I want Shawn to "pay" and I can say that, beside morally right aim for justice to be done, there is a not so ethically justified need for revenge. So yes, you are right, why shouldn't Shawn be happy after all?!
Regarding Ian, you've made me to conclude that I have put myself in position to advocate him which is something he didn't ask. True, he sacrificed but it was his choice. Shown didn't ask him to, he didn't send any wrong massage or misleaded Ian somehow.