Oh, this is a great take! An excellent missing scene, full of believable, painful dilemma and strain -- the load on Severus's shoulders, but also both their dilemmas how far they can go. I love how you put a finger on those very practical dilemmas, those everyday tradeoffs in the face of a horror you can't stop by doing what feels morally right but have to play along to a certain extent at least to preserve your chance at stopping it (knowing that all the while, you will accumulate guilt).