And the distinctions you mention are crucial as well. I can lose myself though sex, drugs, music, intense emotions, etc., but those experiences don’t include a conscious experience of unity. I may experience oneness, but it is unconscious and fleeting.

I’m wondering now if this can also provide us with a key to discriminating between spiritual experiences. How wide the sense of unity stretches, how long the perception lasts, how deep it touches . . . these can all be used to critically reflect on the nature of our own experiences and those of others.

This is a complex subject. I’ll give my view in a very succinct fashion.
Annie Besant once said that the essence of spirituality is “the ability to intuit the unity of all life.” In like manner, HPB said that “spirituality is not what we understand by the words ‘virtue’ or ‘goodness’. It is the power of perceiving formless, spiritual essences”, without being deluded by the gross aspect of the manifested world.
I think a genuine spiritual experience has nothing to do with visions, particular sensations, ideas, etc. It is one where our sense of personal “I” is weakened, if not vanished. That weakening, however, is not product of some kind of psychological pathology, reversion, etc., but a conscious perception of that Unity which transcends the individual.
In other words (paraphrasing J. Krishnamurti), there is spiritual experience when the self is not.