Use a ‘Template Method’ pattern to keep the IO exception handling in one place, based on http://tutorials.jenkov.com/java-exception-handling/exception-handling-templates.html.
Read file with proper exception handling based on the excellent tutorial at http://tutorials.jenkov.com/java-exception-handling/exception-handling-templates.html.
Set lastModified on reload of file (external change) and on property change (internal change).
Introduce Script interface regrouping constants for script properties.