How beautiful and touching. You've captured the mood of the poem perfectly. The speaker's state of mind, his pensive sorrow and silent tears, as well as the finality of his decision show clearly on Severus' face. *admires* His eyes are sad and reflective, he's almost crying, but the tightly pursed lips and deep frown lines tell of determination. It is heartbreaking to see him so upset.
I like how the indistinct setting and the yellow and red colours give the impression that Severus is actually alone, reliving the painful memory of the end of their affair over and over, unable to stop thinking about Harry, despite everything. Harry looks awfully good, self-confident and quite unaffected by what's happened. It may be the poem's influence, but his eyes seem cold and deceitful to me.