I honestly felt you played the matchup perfectly. I think for the first match (which was very close), after you hit Dink with standing 1, you should have grabbed him. Other parts was just firestorm being firestorm, where he touches you and deals a ton of damage and Cyborg has little to no comeback factor haha.
Watching this footage though, seems like the gameplan is to push Firestorm to the corner, then keep him at 3/4ths screen here you can hop over his fireball and punish with diagonal fireball. Keeping him there I think is the toughest part of the matchup, reminds me of the Dr. Fate matchup also.