Squee! However did you know I was hoping for a Snape story? ;-)
This was just wonderful! I loved the way you showed each of the staff apologizing in their own way, and Severus' gritted teeth reaction. And the fact that Filius is smart and perceptive enough not to irritate him, but still get what he wants.
A blossom of hope unfolded in Severus' chest, but he stomped it flat.
Your Severus is perfect here, with all the rough edges and insecurities. Filius, though, is brilliant, especially the way you show him screw up his courage, something not often attributed to him. And the slow build-up -- complete with imaginative duels -- was love.