I take privacy seriously, and I believe your data is yours.
Your data is stored exclusivley on your phone, or iCloud servers, if you have iCloud enabled on your phone. As the developer, I have no access to any of your data, unless you provide it to me in a support request.
When you make a purchase in the app, no data is collected by the app. We are told by Apple that your payment succeeded, and do not get any access to your payment information or otherwise.
Analytics are only collected by Apple if you enabled sending developers analytics when setting up your device. The app collects no extra analytics. If you're not familiar with the analytics Apple provides, this includes things such as app crashes, or launches, but doesn't include any identifiable information.
The only way your data will be used is however you see fit within the app, or if you send me a copy of it to help fix something.