Issue with 'interface' folder means that was problem with proper mod install into flmm. I'm almost sure that second installer file was not installed and therefore all next steps failed. Please check size for crossfire folder in flmm/mods ... there should be missing files. If I remember right, it is possible extract second file by 7zip manually. In bugtracker please search for reports made by (IOC)Wanderer, he had similar issue.