ok I'll have a go
Nature of the attack is quite important here I feel. I realise that this technique is always described this way (as above), but I feel it is important that when practising this technique that the defender should not 'offer' their head to the attacker.
The way we approach this technique, is for the defender to be standing straight, in a natural stance. The attacker then uses a distraction technique (punch to the body, kick to groin, whatever really) to force the defender into a posture where the front-headlock can actually be applied realistically.
I use a finger-whip to the groin (using the back of the hand/fingers) instead of the handsword as this is faster for me, and results in the arm already being aligned better (i.e chambered and your palm facing back) for the following obscure-vertical-elbow strike. The whip also seems more effective in terms of the effect you want, and also has a greater margin for error due to the surface-area of the weapon you have formed.
Might it be risky to use the palm of the left hand to check the attacker's knee? If you are fast enough then maybe you can get your hand down quick enough to keep the knee/leg from coming off the ground - this would be an ideal way to control the attacker's posture. However if the knee is already travelling up then trying to counter this with a palm would result in a broken wrist. Maybe emphasising the use of the outside of the forearm would be an option - this way you keep the attacker's knee from striking you as it glances harmlessly on your 'outside'. Thoughts on this anyone?
Thoughts on turning the head+chin to keep your breathing constant: I've been taught that because this is a head-lock attack and not a choke, breathing is not a major problem in this technique. Rather, the head should be kept facing forwards at all times, because to turn the head to the side actually aids the attacker as he is applying the headlock.
This is how I understand the attack: The attacker's right arm loops over the top of your head then circles underneath. He holds your head in the crook of his right arm, at the side of his chest rather than holding you in front of him. His left arm holds onto right wrist and is 'in tight' against his own body. His aim is to turn your head clockwise (his viewpoint) and to your right shoulder.
When he gets your head to this position you will find it very difficult to move as the strain on your neck is so large you will have to drop your left shoulder to compensate. Most of your weight will be on your left leg and at this point the defence cannot realistically be executed. By keeping your head turned to the center makes it difficult for the attacker to fully apply the lock. If you turn your chin even a little bit the attacker will use this against you and apply the lock.
That's what I've been taught, but I should point out that I've never had to try this out for real, although by training the attack this way it does seem very realistic when we train it in class - i.e. the attacker _really_ trying hard to get that lock on, and the defender executing the technique against a good deal of resistance.
I always used to have difficulty with this part of the technique - always used to get tangled up with the attacker's arms. However I've been taught that because of the way the attacker is typically going to hold you in the lock - with his arms tight in against his own body (he will also be standing more on your right-side rather than directly in front), this elbow-strike tracks straight up on the outside of the attacker's arms and hits directly under the attacker's jaw, and is the ideal strike to be using here.
Also the timing from the groin-shot to the rising elbow is important. If you pause after the groin-shot the attacker may react by shifting his hips back, placing his body-wight on top of you, making standing up rather difficult. I 'bounce' the finger-whip straight to the vertical-elbow-strike as one move. I think about it like this: To be effective, the vertical-obscure-elbow must be chambered by dropping your arm straight down, so that the arm is aligned correctly prior to striking. The fingerwhip / handsword is just something you do whilst chambering the arm for the elbow-strike, it is not a distinct move in it's own right.
We've got an extra move in here. Directly after the lifting vertical-elbow strike (in #2) we pivot (and push-drag if necessary) into a right-forward-bow, simultaneously executing a left push-down block to the attacker's lower centerline, whilst chambering the right fist at the side of our chest. The chambering produces a better structured (stronger) upper-body and provides alignment for the pushdown block.
The effect of the pushdown-block is to check the attacker's height+depth in place, and forces the attacker into a posture with his head in line with our own shoulders. Following on from this we can then exectute the right inward-elbow-sandwhich you describe, to either side of the attacker's jawline.
James