So the coin puzzle actually influences the three main endings?

[Fatmagic]

I thought the last choice actually had a right and wrong answer, but apparently all three coins give you the key no matter which one you choose.

So...I'm guessing that picking the Snake (akin to blaming the disease for everything) gives points towards the Leave ending, picking the Woman (akin to blaming Mary) gives points towards Maria, and picking the man (akin to James blaming himself) gives points towards In Water?

[Peek-A-Boo!]

Yep, you're right

[Vagrant]

This, the Rotten/Ripe apples, the Scarlet/Rust Eggs and the Monologue Corridor. Also, chekcing Personal Items often.

[Settings]

You're right, I actually made a special save just before that puzzle so I could go back and attempt all three answers to see how it affected the ending.