The writing is exceptionally fine, on that we agree.

I just can't see any light at the end of this tunnel for them. As I read this, Scully is in despair, not on the edge. She's so immersed in grief and self-loathing that she can hardly function, and is barely clinging to sanity.

I think of myself as an optimistic person but any story that has a parent grieving the loss of a child feels pretty grim to me, and this goes way beyond that because of the element of sacrifice. She was forced into a decision, into a choice no parent should ever have to make. Sharing grief in my limited experience is better than facing it alone but just barely. This has changed her life forever, and probably Mulder's as well. Humanity is saved but I can't see how they would ever recover.