Okay first off, I can't read what you're doing with the hyphens but it's not marking off the iambs. Secondly... are you saying that the "e" at the end of "Dulce" is invented, or is it a typo?
Thirdly I would contend that the line break after "est" is brilliant. Re-read it. The lie is separated from the cause... the penultimate line identifies "the old lie" as
"Dulce et decorum est"; Owens then completes the quotation in the final line.
But by placing the line break, as he does, after "est," he's saying in a war poem "It's always a lie to say 'it's sweat and right' when you're talking about death." It's clear from the poem that it's death in war, specifically by gas, that he's talking about - but death itself is made more prominent by pushing "to die for your country"
(pro patria mori) to the end.
Paradoxically,
pro patria mori, in the sense of the whole of the poem, is greatly strengthened by the placement. To title the poem "It is Sweet and Right" rather than "To Die for Country" lends the whole a haunting irony made all the more bitter by the division of the two phrases.
At least thass what I think, but I had no jesuits to guide me