Once you have created the code page, you can get a link to the page by clicking on the "Preview this page" button in the Pages screen and copying the url of the pop up that appears.
Once you have the URL, you now need to create a Formula - URL field in the table where you want to embed the page.
Paste the URL you copied in between two double quotes into the formula builder and make sure the Embed as iframe in forms checkbox is checked:
Place the new field on the form wherever you would like the codepage to show.
Sure!
This will be similar to how you can include a CDN into the head of an HTML file, using the script tag:
In the src attribute, include a link to the module.js code page. This will load the js file before it loads the rest of the html page.
If the js file doesn't solve your moustache problem, you can add a link to their CDN. Here you can find all different versions of the project and their CDN:
https://cdnjs.com/libraries/mustache.js/4.2.0
