Thanks for the explanation. The search in content of 404 page is the default WordPress widget, which is not affected by settings from Theme Options.
The functionality of this search can be changed via additional customization in files. Additional customization is outside the scope of our basic support. You can try it by yourself if you have PHP skills, for example, read this article – https://thomasgriffin.com/how-to-include-custom-post-types-in-wordpress-search-results/ , or hire a developer for this.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.