I am not familiar with the tune that you refer to, so I most likely cannot accurately critique your poem. But as I read it, I have a few thoughts I will pass on.
The meter… A theme has to be very clearly and compellingly developed to really hold the attention of most hymn singers through 14 syllables in a single line. Even pentameter, which is my personal preference for writing, is long for singing.
The theme… the darkness, despair, turmoil, meaninglessness… that results from a rejection of truth, is a powerful theme. It is suited to a long and ponderous meter, yet to be singable has to be kept free flowing and alive. I love writing (or trying to write) about these deep questions; I am not the poet for writing about sad goodbyes and blue skies and flowers in springtime. But the difficult trick is to capture these deep themes in easy words.
I would probably continue to refine with a view toward eliminating more of the trite expressions (alas, anon, vertigo, woe betide, yes, lone) and redundancies (lone, alone, hopeless, without, friendless, no one). And possibly consider changing the metrical arrangement, unless of course you want it to simply live as a poem instead of a song.
There’s plenty of good material here; the key is going to be the polishing.