From the above tutorial on Ghost’s website, it specifies how to create a custom post template. But the file being linked to is broken, since the GitHub repository is probably private.
Is it possible for someone to provide custom templates, e.g. the one references in the tutorial?
At first, rename it as custom-full-width.hbs file, i can see you used capital C. but using small letter in file name is standard.
Then make sure you used {{!< default}} at the beginning of your custom template file, so all the scripts and default code will show in that page.