Gigabit Ethernet full-duplex is actually 2Gbit/sec counting both ways?

Full duplex means bidirectional communication. So yes it could in theory reach 1 gig up and 1 gig down, but the device transmitting up or down would still only reach a max of 1 Gpbs.

Reaching the theoretical max would also depend on the NIC and other hardware such as drive IOPS. Don’t hold your breath too hard if you don’t actually ever see the potential bandwidth being 100% utilized.