Hey, another CoC fan! I wrote a dialogue with a similar concept ages ago -
Minotaur Cum Addict. Though that was for the minotaur bad end rather than the gloryhole scene.
The reason the Chapter stuff isn't working is because you never declared it as a variable. So it checks if Chapter is set to 0 and always fails, as it was never set to anything at all).
To fix that you need to have the line
initial_settings:{"chapter":0}
I'm fairly sure you should also just be setting it to 1 instead of trying to add 1, as even if you're planning more chapters it'd make more sense to only be able to move to specific chapters instead of just moving to whatever one is next.
Stylistically it's weird that some of the narration is Him and some is Thought. If the Minotaur isn't speaking it doesn't really matter which one is used, so just stick with whatever one looks better (probably Him).