Couldn't keep well enough away - the final steps were kind of captivating my mind a bit but I couldn't seem to put them together - hope you don't mind but I ended up file diving/editing to get the blood key. Having gone through the endings now I figured I'd write out some more questions/comments:
I was wondering if the bug with the organ also applied to the song from the nun, as it seems like it wasn't triggering whatever event is associated with getting you the key. Do Re and Mi correspond to the left, middle and right of the organ, correct?
Also, the vending machine - where is the code for this actually provided? I dived this in the end to get the ending there, but I imagine I overlooked it somewhere.
The storybook seemed useless at first, but is it intended to hint to how each ending is achieved? This was my first thought of how to get the code for the vending machine but it ran dry.
In the underground, I interpreted three of the text pieces ("ocean springs forest", "end as we began", "twins apart") to be a start and end of yellow with blue then green in between, which gives you the monster eye. This seems like intended progression, but is this what you intended? I also did not find a use for the other two - something like "shining sun turns the sky blue", and "no red". Are these just red herrings that are meant to be mixed in with the real clues? I guess a full read of this could be "start matches end, with two progressions of yellow->blue and blue->green, where two separate parts of the code are both yellow and none of them are red"?
Earlier when I was still figuring things out I brute forced the Knight Outfit code by accident. Is this shown anywhere in the game? I will admit I did a lot of unnecessary reading-into just about ever set of four colored items I could find which was kind of fun when I realized where you had placed some of these in the town.
It was interesting tracking down the NPC that triggers the night 'betrayal' sequence - and making sense when they appear in that ending and appear to the be the same one with the diary in the mole key room.
There is an NPC that seemingly shows up at the bar in town to talk about the red faceless guide NPC - he isn't in every game, this is random or triggered specifically? Just like the 'flash of memories' as you enter the cave sometimes appearing.
Either way I think I ended up spending far more hours that I ever really expected to on this game and do hope you'll pick it up again in future - it reminds me a lot of a certain genre of DOS adventure games (Defender of Boston, etc) where the mechanics of the game can only be discovered through extensively investigating all aspects of the game to exhaustion, and each step I figured along this process felt rewarding due to it being 'just out of reach' until I managed to put enough things together.