Just completed the game - how much did I miss?

I just got to >!Room 46!< after being hooked on this game the last couple of weeks, but having done I feel like I might have missed a really big chunk of content and/or plot context.

I suppose I’m not really asking to be told what I’ve missed, so much as confirmation of whether I’ve missed so much that it’s worth post-gaming a lot more or if it’s just a little bit of flavour plot that I can just google?

Completed on approx day 125

!Only found one red letter (VII)!<

!Never figured out tomb - statues function and/or how to get the tunnel connection!<

!Never connected lab and boiler room!<

!Don’t know what 4th permanent outside fixture was (I had orchard, diamond mine, and outdoor room)!<

!Never got freezer close enough to furnace to defrost the chest freezer (but I did get the secondary room so understand there is a server room somewhere in the grounds)!<

!Figured out the floor letters, but cracked zero safe codes (except the orchard gate)!<

!Still at least one safety deposit box in the Vault I hadn’t accessed!<

!Missing room 008, 019 (I presume one is the exam hall)!<

!Never got a Gallery name right!<

!Never fully completed a Chamber of Mirrors!<

!Figured out the music sheets, but not what they referred to!<