Ask HN: Advise on monetization model for my freemium app wanted

I'm an indie app dev and looking for some conceptual help with one of my freemium apps. I'm thinking about completely restructuring the business model i.e. the placement of the paywall and what amount of content stays free and what'll move behind the paywall. To be clear: This isn't meant to be a hidden advertisement for my app. I won't even tell the name (if not explicitly asked for in the comments). Just for enough context: It's a low-stimulating, stress-free coloring game for children - especially for neurodivergent ones (e.g. ADHD, autism). There are no ads in the app. Images are colored by simple taps and swipes. No mistakes possible. --- The situation: The app is around 1 year old (in the Play Store; it's in review for the App Store rn). It had 3.5 k installs. There's a premium in-app purchase - one-time, not a subscription. It costs 6 $. During the lifetime of the app an amazing amount of 4 users bought premium. That's a conversion rate of ~0.1 %. And also the app only received 5 ratings. The app is divided into "worlds": Themed level packs with 10 levels each. One level can be finished in 10 - 30 seconds. There are 20 worlds rn. Every second world is a "premium world" that