Evolution is exactly as I stated. The theory of evolution (which is actually misnamed. It attempts to explain the diversity of life, not evolution) is that evolution has led to the production of all of the many species of life present on earth. The theory is that evolution produces new species. This has been observed in the lab and in nature. In your example, if there are now more organisms with an imperceptably moved jaw than there were centuries ago, then it is possible that this movement DOES confer some advantage to the organism (even if we don't know what that advantage is.) Your example is an example of evolution. What I have stated is one possible mechanism (believed to be a fairly commonly occurring one in nature) of speciation. I don't claim that all speciation events occur via this mechanism.
Well this is exactly why there is so much confusion on this subject. If I asked "what is evolution" I would get several different responses. I would get your response, which is perfectly reasonable. Then I would get the Natural Selection answer saying that evolution occurs in response to catastrophic events, and only those species that adapt and survive are able to live. And then I would get the genetic drift answer saying that natural selection isn't necessary for a species to evolve.
The main reason there is so much argument on this subject is because everyone is arguing about something different! Personally my opinion on Darwinian evolution (as it's spelled out in his book) is that I'm skeptical. I'm not willing to say evolution doesn't happen because that's absurd. but at the same time I'm not willing to say that everything happened due to random chance because that, IMO, is equally absurd.
Can we get a unified theory of speciation? Is that too much to ask? :)