All I have to say is most of your points are accurate save for one. The TMA guys preaching one-punch kills. Single-blow killing techniques have been around for ages, but almost none of them focus on a punch or blow to the face or skull, the idea is not to impact bone, but other areas where the probability of killing or crippling is much higher. One of the only sure-fire techniques I've heard of concerning this is a blow to the throat. More times than not if you land it on an unsuspecting person (meaning you do it out of nowhere, before the fight begins, so fast and so hard that they do not see to defend the target your aiming for), more times than not the crushing of the larynx will result in death. I have a friend who actually did this to a person in England when he was younger and spent some time in prison over it.
I've heard rumor (rumor because how does one really observe these techniques?) of older Martial Artists being able to stop a heart with a specifically targeted blow delivered with also a specific amount of force. The problem with the inconcistency of application of these techniques is not because of fault with the techniques I don't think, but because of lack of opportunities to properly demonstrate them.
Most street fights are spontaneous, and typically there's no real gameplan as there is with organized competition. So it's sufficient to say nothing in a street fight can really be controlled. Hell a grappler who is simply trying to choke a guy into unconsciousness could end up killing him by accident, or because of resistence from the guy, breaking his neck. A wrestler going to slam a guy could also slam him and cause severe spinal injury, paralysis, and even death. But when your physical well-being is on the line, preservance of your own becomes the priority, not the safety of the opponent, therefore people who routinely get into these situations don't have any real means to gauge what kind of control should and should not be used. You don't want to hold back because you could get hurt. You don't want to go balls-out because you don't want to end up in Prison, but Prison might be a better alternative than the hospital or the morgue. And usually you have less than a minute to consider all of this.
Only the most experienced, and lifelong practitioners of Martial Arts in-general have I ever seen remain calm, and approach these situations with organization. Anyone can argue their response would be extreme if the guy ended up with a broken leg or something, but the Martial Artist would then say something to the degree of "I could have killed him, he's fortunate." Just to remind people that this situation was about their physical being under threat of imminent harm.