Awww... this is wonderful! I love being shown the present and the past together, and I especially love the New Year's Eve scene, when they were watching the fireworks outside. You did a wonderful job with both Snape and Harry here -- a less bitter but still sarcastic Snape with the same dry humour that I love, and a Harry who's every bit his Gryffindor self even in an alternate reality setting.
This is such a magical story despite the absence of wand-waving. I love it!