You were technically halfway done with the fight, but the second half is harder.
As for healing yourself prolonging his attacks one turn, that's exactly it. you have to attack a certain number of times, because attacking is when he runs through his dialogue, and the fight is only done once he finished all of his dialogue.

You were roughly half way done

Aw jeez. Must I keep attacking or is healing myself fine? Or is healing myself prolonging his attacks one more turn?

you need to attack him in order to advance the fight since making him dodge is what is tiring him out.

Keep attacking and try to wait to heal when he gets to the sparing part. You can heal as much as you want during that