Yes, as long as it has a FC connector. Some drives require an intermediate adapter. Seagate drives require an adapter that converts their proprietary 80 pin connector to a 1x3 differential connector. No, the application informs the driver that it wants to transfer a certain number of MBs, then the driver partitions and DMAs the data to the drive through the FibreXpress card's buffer. When the transfer is complete, the driver informs the application.
All intermediate transactions are transparent to the application.
They are assigned when the driver is installed. No, not physically, but there is a limit of 126 concurrent nodes set by the FC-AL standard. Not through an arbitrated loop, but the data can be copied to multiple nodes through a LinkXchange LX1500 Crossbar Switch and then be sent out almost simultaneously. It is currently all 5 volts. A voltage regulator on board takes care of the 3.3 volt components.