Getting FTP (which has been around since what...the early 1970's? largely unchanged) to work, correctly, behind a modern, NATted, router/firewall, can be a serious challenge for people not familiar with some subtle aspects of networking. You will be MUCH better off using SFTP (instead of ftp), which is part of SSH. Not only is it more secure, it is also a protocol invented since Reagan was first elected, and plays much, much, much more nicely with complex network situations, which most of us now have in our homes with a WAN/LAN gateway/bridge/router.
If you INSIST on doing that (I think it's stupid), you'll need to read up on "passive mode" vs "active mode", and you'll also have to forward the DATA ports as well as the FTP port. (See? It sucks)
You'll want to use ssh-style SFTP, really, and turn off that FTP service. The ssh daemon in FreeNAS is already configured for SFTP. You'll only have to forward one TCP port, and there is a wide variety of decent software out there that will access the SFTP very nicely and easily. I suggest "bitvise ssh client" (which is great, because it does all the SFTP stuff, as well as providing a superb ssh command-line interface log in) for Windows, or FileZilla. For your Android phone, I recommend AndFTP, which also handles SFTP nicely. The process is much, much, much easier to set up than FTP (in fact, what you've done already would have been the correct procedure, had you been using SFTP via sshd instead of FTP via proftpd on your box.)