An interesting argument. In the sense that these things are abstract and exist purely as human conceptual creations they can certainly blend and overlap. Obviously comparative religion or anthropological studies more precisely define these terms but, of course, arbitrarily.
At this level spiritual ideas, beliefs, rituals are individual. I think limiting religion to group rituals based on shared beliefs is very workable. Individual beliefs, if they exist at all, are very much secondary and often suppressed. This is a thought control process that shapes group actions by creating a space for group actions subject to approval. This space can be larger or smaller and allows a range of actions for a subgroup that allows ranking those individuals on the basis of the extremity of their actions. There is no independent moral or ethical criteria for these actions and rankings because they are divorced from personal, i.e. spiritual beliefs. This, of course, is based on evolutionary ethics inherent in the social nature of our species. From this it is easy to see how dangerous religion can be. Dangerous or socially beneficial is then a result of some leader or lead group’s adherence to or movement away from evolutionary ethics. Individual ethics based on personal spiritual “feelings” are normally repressed for all but the leads.
The common recognition of this is the under lying reason for the steady and now rapid decline of religions. At the same time all forms of spiritual belief and personal ritual are being accepted and rediscovered. These are open to evolutionary ethics and usually less potentially destructive. Most people don’t, I think, work this out very far but they sense it and so are now instinctively more open to spirituality and much less open to religion. So they make a personal distinction hence the continuous debate. This is good. In my view religion has become a maladaption and represents a disease vector.
Spirituality, in this sense, as individual allows free diversity of personal belief and is a natural adaption for fully urbanized and networked social animals. But this diversity must be protected by our emerging planetary social structure.
The evolutionary nature of our social ethics is now well beyond our biological evolutionary nature. As Stephen Hawking has pointed out our evolution is now externalized and knowledge tremendously extends information in our DNA. This is also a major factor in our change. But that is another discussion.