I wonder if you've thought about adding
inside the div.verse in the CSS?
I find poetry tricky in epub, because the visual impact is so much more important than for prose. I like a generous left margin for poetry, but dislike line breaks. Often I enclose the poetry in an outer div and give a small percentage as a left margin, so I get a little air around the text which adjusts with the size of the screen. A narrow (but nice and readable) font can also help things. While I've just given up on making poetry books for Kindle.
A propos visuals, personally I find the backlink to the table of contents after each poem unappealing – it sorts of buts in just as you sit back to reflect on the poem. It would improve matters if it was put (unobtrusively) at the head instead. But that may just be me...