Yes, you can run an FTP server on any IP number, be it dynamic or static. The key is that your clients know what the IP is.
In my experience and my opinion (and thousands of others), IIS FTP is a joke. Yes it has basic FTP functionality, but lacks the features and security that other 3rd party FTP server's possess.
Try Serv-U FTP Server and you will be more than happy.
There are other good ones out there, but I recommend
Serv-U.
Good luck!