I almost wanted to be angry with Ginny and Harry for separating, just because she was so very single-minded, and he so very taken with it that he never realized something was not right; but then I realized how very real that was and had to read what you'd done about Harry & Severus.
I'm so very impressed that a story written entirely from Harry's perspective manages to catch so much of Severus' inner workings; his constant paranoia about manipulation (justified, of course), his pessimism towards anything that makes him happy.
Which is not to say that Harry's perspective is not just as revealing of himself; Harry is very correct in his assessment of himself as being caught in the moment, and lacking introspection.
We see that even in your description of Al and Scorpius through Harry's view; in the orange peeling scene, we see that Harry is just barely perceiving their romance, although he's been seeing the evidence long since (ie. he notes their reactions to each other just before, and in the aftermath of, the curse unleashing, among other instances).
You know, though, I had expected camels to be the quadrupeds of malice in this story, given the title. Well, can't have everything ... the ending is perfect, closing the circle of the story and illustrating how well suited Harry and Severus are, not just because they have a child together.