I forgot to ask what sport you are training for. That's pretty important information and may make a difference in how you teach the exercise. I'll assume you just want a basic Sch. B&H.
(Disclaimer-I don't train Sch. and am new to the B&H myself)
It's obvious that the dog wants to bite, and kind of understands that barking is what gets him that bite. I would work on teaching him that the ONLY way he's going to get that bite is to perform the exercise correctly.
In the first video the decoy moved too much before the bite. While a little movement can be helpful to help the dog maintain intensity later, at this stage I would want the decoy to stand like a statue. The bite should only come as a reward for controlled, rhythmic barking to "animate" the decoy. I would have him stand with his back to a large stationary object to make it harder for the dog to push him around.
In the second video it looks like he anticipated the dog taking a dirty bite and he actually moved to avoid it, which only reinforces the unwanted behavior. It's up to you to handle the long line so as to immediately correct a dirty intial bite. You need to see it coming and if necessary correct the instant before he puts his mouth on the sleeve. At the same time an untimely little flinch from the decoy will undermine your correction. Handler and decoy have to work together with perfect timing.
I would go back a step or two, put the dog in a sit square in front of the decoy (have him stand completely motionless) and give your B&H command. Stand about six feet from the dog to make it easier to handle him. As soon as he barks twice in rythm I would have the decoy pop the sleeve and attempt to flee backwards. That can be extended to three barks, then four. It should be a very black and white picture in which the ONLY thing that produces a bite (or any motion from the decoy) is clean, forceful barking. Once I get a consistent clean bark I like to have the decoy intermittently give the bite so as to keep the dog on his toes and in high drive.
Once he understands that CLEAN barking is the fuel that gets the decoy moving it will be easier to send him from a little further out without him molesting the decoy.
I'd like to get Nelson's opinion on this one personally. He's an actual trainer (I'm not) and could offer good input.