I'm a little unfamiliar with "FFC" as this was a new thing hacked into the system for the pandemic since people didn't understand what it meant to cancel a ticket.

How did you get the $360 FFC? I thought it was by changing the return which resulted in a lower fare, so the $360 was a residual. In that case I'm surprised it isn't already an ETC or equivalent - yes, I think making it an ETC would make it easier for you to tender it for the fare difference. Someone else who has more experience changing flights since 2020 might be able to comment more.