Perhaps you could have wired/wireless solution to cover entire area and minimaze the spending.

Did you have the issue resolved?

Do you use a Passive FTP mode on the client?Also you could do a capture on the ASA in order to see the connection.

Do you have a border router with a firewall and if YES, who is doing the NAT?

Yes, you are correct! You don't need a single mode fiber and SFPs, they are more expensive. 1000BASE-SX SFP will work with a multimode fiber patch cord.You need a SFP for each end of the fiber. Just make sure the SFP is supported on your switches.Mor...