When you are lunging, the proper way to stop a horse is to switch the rope to your other hand, slide it up, pull it the other direction, and step your foot forward as if to block him. If he still wants to go, let him go. Be more aggressive and when he wants to stop, keep him going just a few laps longer. Show him you're in control of when he stops and when he goes.
I would attach a lunge line to him. When you want him to stop tug slightly on the rope and start backing up. Cast your eyes down and make yourself look dm
If he does not listen to you, continue to langue him until he knows that you are in change of his movements. It may take a long time and he may do it because of burning out, but that is what works for my ottbs