What I got out of it:
1. The past is never gone. Even the worst things (Nazis) will return.
2. There is power in real leaders who build consensuses in third followers, but corrupt leaders (Markos) are destructive at best and parasitic at worst.
3. Guilt and shame are necessary feelings, but be guilty and shameful about things you can fix or else they're inert (the Doctor).
Also there's something about breathing being a primary concern with Susie's mother and Susie's eventual identity as Mother Suspiriorum being the mother of Sighs.