The FAS3210A (2 controllers / 1 chassis) has 2 FC ports (4Gbps) and 2 SAS (6Gbps) onboard (on each controller). Additionally it has 2 PCIe expansion slots (on each controller ), which can be populated, in your case, with 4-port SAS adapters and 4-port/2-port FC adapters.
I don't know precisely, but I guess you could use them all for NDMP.
It would be better to have a SAN to connect of all of those devices: netapp storage, tape drives and the media changer (robotic control). If you dont have it, you will need several FC ports to connect the drives and MC to the netapp controllers.
Yes it is ok that the netapp controller owns the media changer. And as Radek said, you better use a third-party software to manage that environment.