The mod launcher does install df like that. It uses the second folder for mods that have different versions.Or are you double-nesting folders on purpose?
Is the mono-2.0-bdwgc.dll file in there in the right place? Also, exclude the Darkness_Falls folder from your antivirus software.Unable to load mono library from C:/7D2D/Alpha19/Darkness_Falls/Darkness_Falls/MonoBleedingEdge/EmbedRuntime/mono-2.0-bdwgc.dll