Just because you've managed to cook a medium-rare steak perfectly once or twice it doesn't mean you've mastered it. Zoro didn't even know what he was doing, Enma kind of did. Pure luck
We don't really know how lunarian powers work and I wouldn't trust King's judgement on any matter. The guy started fighting with his flame off for no reason
I never said he mastered CoC/ACoC, but that doesn't mean he can't control it. Zoro showed us he can control that power against King. He just viewd it differently. He see it as CoA and CoA 2.0 instead of CoA and CoC. Control is still control.
Enma didn't help at all. It only forces the user to release CoA. It has nothing to do with CoC. Nor does it affects his other swords.
King did not turned off his flame mode for no reason. He turned it off because he wasn't confident it would protect him from Zoro's AP. Zoro even called him out about it. King response wasn't Zoro couldn't damage him in flame mode. Instead he said Zoro can't beat him because he's human.
King turning off flame mode to increase his speed, increasing his distance, and attacking with a long range attack increased his chances at evading Zoro's attack. That was the smartest thing to do in that situation.