Beliefs can lead to harmful actions though, that is why people can be locked up for "delusions" or "beliefs that can lead to harmful actions" in the first place. Your definition doesn't really address the idea that ideas can be harmful and that we do actually disallow certain beliefs in society.
As for your definition of religion, I think it is entirely relevant, as you suggest my ideas on redefining Christianity to include a gay Jesus is offensive to religion. Well, if you are going to claim that, I would challenge why this religious belief is less sacred than the traditional view of Jesus according to Christianity. How do you define religion is definitely relevant.
As for the last comment of it being DSM-V, what does that matter when referring to it as DSM-5? As far as I can tell, it is not a meaningful distinction. Do you disagree with the idea that religion has a specific exception in the current DSM when concerning religion?