I read your post Jean, that sucks.
I wrote this a while ago, and a lot is out of date (Parse doesn’t even exist anymore), but some stuff is still relevant. It’s still a lot easier to learn stuff in Mapbox vs Contentful/Prismic. I haven’t used Prismic in a while, but I’m using Contentful quite a bit.
From the looks of how you’re using Contentful, Jean, you’re far beyond this, but it might help someone else: https://github.com/javaporter/mm4-contentful
Contentful_Middleman has more examples now too.