Hey, just a few points: while working this drill (considering that the attacker had the knife in his right hand, around your neck on the left side), raise the right arm behind his right elbow, reaching up and over to almost touch your left ear, so that he can't pull the blade across your throat. Pin the knife hand to the chest with your left hand. Lift the right arm and turn slightly, stepping with the left foot on his right foot. Stomp if you like. That way, he's not able to move that foot and he's less able to deal with your counter. Then, as you rotate under his right arm, drive the elbow of the left arm (the knife pinning arm) into his right hip joint, the Booj folks out there refer to this point as Koi, if I remember my Gyokko Ryu kyusho correctly. This will break his balance even more. Now, the underarm pass and transition to your counter (elbow bar, hammer lock, disarm&dispatch, etc) with no resistance.