Beautifully-imagined and written -- painful and dysfunctional, and yet you show exactly how Petunia has made everything work for herself: everything so thoroughly compartmentalized and denied and yet. . .
The inferno-like scene in the pipe is very effective; I can see Severus behaving like this, can see all of them, in fact. None of them is likable, but nevertheless, my heart aches for them all.