Don't know that much about directory loader, haven't used it for production, just tested it.
But for the file size: I would try to load the file manually, if that works, it also should work with directory loader, I think.
But if this is the one and only file, and it is possible to load it, why should you use directory loader?
IIRC directory loader loads the files into memory just like you can do it manually, but it does it automatically. So if you only have one file, ore even more than one file that all together fit into memory, you don't need directory loader (except you want to change files on the fly). On the other hand, if the files don't fit into memory together, you must split large files and load them one after the other while unloading the older ones, after you have executed the one that's loaded into memory.