Contribute to the guide at the GitHub Page
The foundation of this guide is based on Zachary Kjellberg's Dark Souls 3 Cheat Sheet source code, which was in turn was based on Stephen McNabb's Dark Souls 2 Cheat Sheet source code.
You can visit the GitHub repository and report Issues or create a fork and submit a Pull Request.
Yup, use the profile selector and buttons at the top right of the page to setup multiple profiles.
The checklist is saved to your browser's local storage. Be careful when clearing your browser's cache as it will also destroy your saved progress.