Actually I think that dent was on the chrome before the motorcade even began.
No, that myth was debunked years ago. There was no dent in the window chrome before the limousine drove through Dealey Plaza. There is film footage of the limousine taken shortly before the Dallas motorcade that shows the chrome was not dented.
(the segment on chrome bullet dent starts at 3:12)
The people who saw the curb mark first, including Deputy Sheriff Walthers, said it clearly looked like a bullet strike.
The fanciful trajectory that has a bullet fragment exiting the skull at a high enough angle to clear the windshield and the roll bar makes it impossible for that fragment to then magically nosedive and somehow still have enough energy to chip the curb or to cut Tague's face.
Yes, bullets can curve when they transit gelatin blocks. What do you think happens when you put skull bone around the gelatin? Any bullet or fragment that plows through the back of the skull, transits the gelatin/brain, and then plows through the skull again as it exits is going to lose a large amount of its velocity, and then it would have to somehow get over the windshield and the roll bar and then nosedive in midair to hit the curb or Tague's face. It's just silly. Even Posner recognized that the idea that the Tague curb mark was made by a fragment from the head shot is ridiculous, but his alternative theory is even worse.
There is just no plausible explanation for the Tague wounding that does not involve four shots. The fragment--whether metal or concrete--that hit Tague's face struck hard enough to sting him and cause bleeding.