Thank you for your post.
I have seen several FileMaker Pro files with customized help. One method is to have a button/script that switches to a layout with the help information. A return button executes a script that takes them back to the original layout. As you can imagine, in some of these cases, there were a lot of layouts. Remember, in Layout setup, you can uncheck the option to "Include in layout menus" so that would keep it inaccessible by the user unless it was specifically called by the button.
The other option, if the Help is going to look consistent across all help topics, is to have a link to another table based upon some "key" field. When the button is pressed, it links to the other table, switches to one layout that displays the help topic and a way to return. This would only allow you to enter the help information in one table and then reference that table/layout/record.
I hope this helps.