I think I shall start here with adding feedback to the stories I have read in the fest, it seems fitting.
What a beautiful story.
There is a lot here, from the idea of taking Lily's point of view through to the use of horcrux-baby-tom-harry, through to the little set for watching the different lives of those living, both is and what could be. All of them are fascinating in their own right and articulated in a twisty, flowery, original-simile way that makes for spectacular visuals, feeding my own delight on word play. However, I think perhaps I was most enarmoured with the way you used as both plot and emotional crux, a few observations that have always struck me about the HP books. Snape has always been the main connection of his parent's generation to Harry - Sirius was too fleeting to ever really assume it. A complicated connection for sure that does more damage than good, but one that was completely confirmed by his patronus and childhood. By the end of the series he is an embodiment not only of Dumbledore's failures (Tom, Snape, Harry - Harry being the most successful), the failures of himself and his generation, as well as that of Voldemort, but acts as the key to the past and future. He had to die, because they were the past group and he did not fit in with the new, and Harry could never really grow beyond the child potential with him there being a figment of the errors of before ...at least according to the structure. So basically what I am trying to say is... I love how you have used this so beautifully to bridge between the afterworld and Harry, but managing to tie up those knots that were left undone in canon, and tying them up in a way that is bittersweet, and includes Snape without just jamming him in for no reason other than a sense of 'but I like him!.'
The relationship between Snape, Dumbledore, and especially Lily is ... like giving water to a dehydrated person. Even beginning to address those currents that swirl around all of them is such a mountainous task, but you do it well. I like Lily's slow realisation of her own feelings, and her reconciliation with the events before her death and those that are happening afterwards. It reflects nicely the way in which she is the lynch pin in so much of the story .. and everyone tries to deal with the ramifications of her death and actions, and by everyone I mean Snape and Harry, as well as Voldemort and Dumbledore. Sometimes I think Lily's observations of Snape are a bit too close to the authorial voice (too much defence of his miraculous skills which clashes with her harsher opinions and makes the cumulation of the ending a bit ... tricky to believe.), but this is forgivable because having her voice there at all is so lovely.