Filemaker cannot embed fonts except in PDF files. You are using the simplest way now for non copyrighted fonts.
From Filemakers DocumentationYou should use a custom installation program to package your runtime solution for installation by users.Configuring a custom installation application to install runtime database solution files may require moreengineering than using a compression utility, but will help to ensure that your users do not have difficultiesinstalling your runtime solution.Here are some custom installation applications you might want to use:MindVision Installer VISEInstallShield MultiPlatformMacInstallerBuilder
While I agree that you will need a custom installer on Windows on a Mac they cause too many issues compared to a simple drag-and-drop dmg installer and should be avoided. Copying the fonts into the user's font directory upon first run is the correct way to do it. You can check if the fonts are still present in the directory whenever the runtime is launched or the layout is accessed. Any Mac software installer will be unable to check if the fonts have been moved once the installation has been completed anyhow.
How would you do this check to see if the fonts are in the fonts directory?
Use the following path:
Left(Get(DocumentsPath);Length(Get(DocumentsPath))-10) & "Library/Fonts/" & "Font Name.ttf"