I'm torn with this one. I think you crafted an exquisitely angsty tale, and did a wonderful job of showing the complexities of the infidelity, the reasons why it would come about and the pain it would cause all involved. This Harry deserved to be thrown out by both his lovers - all of the things they accuse him of are true. This character needed to be brought to the low point he was in order to move past his immaturity and reconcile who he really was, before he deserved to have a relationship with either Ginny or Snape. I liked that Snape didn't just take him in when he made his choice, but insisted that Harry work through his issues first.
I thought your characterizations of most everyone in the story were great, from a sympathetic portrayal of Ginny, a nice balance of snark and vulnerability in Snape, a lovely Neville, canon Hermione and Ron, to nicely developed personalities for the kids. For me, the notable exception was Harry, and that is what I'm torn about. Yes, he's incredibly reckless in canon, and doesn't always think through his actions. His recklessness, however, was almost always in the cause of doing what he thought was the right thing at the time(and not just right for him), so it's hard for me to accept a Harry as selfish and self-involved as the one depicted in this story. Aside from that OOC nature, however, I do think the story was a gritty, realistic exploration of the struggle of someone accepting their sexuality and the painful consequences of infidelity, skillfully written.