Have been away in the wilds, but weighing in on Dim Mak ...
* first, I've studied 'exotic topics' along with mainstream. In traditional Chinese medicine, I studied under a renown Taoist/an MD in both Chinese and Western medicine. In our 'master class' he offered PhD with a top US university. I've experienced personally incredible things, along with noting credible physical healings with 'qi gong' and 'miraculous' healings in the Christian faith that were verified by teams of MDs in terminal cases.
so, IMO 1/ all humans have abilities built-in but rarely utilized
2/ it is possible that a rare person could conceivably tap into the ability to 'kill with a touch'
3/ however, I think it very very improbable that a 'dim mak expert' would use such a power to kill ... he would know it would be easier to kill just by poison, for example.
* A few months ago I read a book by Grant Morrison 'Supergods'... he's one of the top graphic writers, writing on Batman, Superman, etc. I've never read his novels, but this book is a good read for anyone interested in pop culture. A segue: if Batman were possible, Bruce Lee would be the closest to the physical Batman.
*anyway, two of Morrison's stories: He comments on the bio of a mystic/world traveler. He went to a Tibetan cave that had been the home for years of an ascetic. This guy had left his handprint in the rock face, deep into the solid rock. Of course, one could say that was faked, maybe the guy brought in putty. However, for now I take it as example of the strange but possibly true. I can't easily laugh it off, since there have been many strange things in the world.
* Morrison also recount the time he was in Los Angeles for a comics convention, brainstorming with a friend late in the night on a current Superman project. Their motel overlooked a railyard, and they went out for fresh air. They saw two men approaching, and one was dressed as Superman; actually he writes this was the 'best' Superman he had ever seen. He asked to talk with 'Superman' and Superman responded with a straight face. He even 'sat like Superman.' Of course, this was a comics convention, so you would expect a Superman to walk around, but a 'perfect' Superman at that time of night with few people around is just a little example of small intentions. Many of us have had experiences in such incredible 'coincidences' that were marked by an intention. I believe this is a prime way the universe works, and I say that from experience.
* we see this in the emerging studies of quantum particles, where space/time are irrelevant; a person can affect 'the universe' with intent. Bruce Lee himself is one example, bringing his positive dreams to reality; on the negative side, he also believed he would die early / that he hated the thought of aging.
* Now, while I say it's possible, I also doubt any true Dim Mak expert would use it to kill; he would instead use it to heal. He would know to kill someone is to basically kill yourself both spiritually and physically. He would have little use to kill a person out of jealousy, for example... jealous of Bruce Lee or whatever. If such a person lived in that era, he would be one in six billion. One might argue maybe there could be one evil Dim Mak person, but I don't see this. Even an evil DM expert would understand what he would be doing to himself.
* to wrap it up: you can test negative DM principle for yourself. Send evil thoughts and emotions to someone you hate. See how difficult and scary that would be? To do that for months and months! Likely, you can accept the possibility of such death thoughts you send would be 'chickens coming back to roost' ,,, I myself have experienced people who were spiritual 'haters' for years and years, and destroyed their lives. And imagine, saying "I'm going to kill that Bruce Lee with my touch of death! Now I prepare!" That would be a real terror filled existence.
* So I don't believe Bruce was killed by Dim Mak.