I think this was really a terrific piece! The Gothic atmosphere kept it from getting too melodramatic, and lent itself to the pacing and the relationship. With menace around every corner, it's no surprise that they were clinging to one another.
It really worked well, from start to finish. I loved the Jane Eyre imagery, and the ending was spot-on. Your Harry was innocent and vulnerable, but you gave him an inner strength that kept him from being a victim with Snape; difficult to do in chan. I admire your deftness!