What, you think the force dissipates in the jaw due to it's structure, like with some sort of doggie-crumple zones?

The jaw is attached to the neck. The neck is attached to the spine. The spine is attached to both sets of legs, which are how the dog gets traction. Or does the force get transferred from the jaw to the dogs tippytoes with fairydust and magic, maybe?

Also, do you understand how levers even work? The pivot you talk about is completely irrelevant. Force applied further away from the fulcrum, which in this case is where the dog's neck is anchored to it's body, has more mechanical advantage. Closer to the fulcrum, where the neck is anchored to the rest of the dog's body, means there is less mechanical advantage. There is no way a leash is going to do more damage closer to the neck. And no, the lever doesn't need to be rigid. The same principles apply.

If we look at people doing the same thing, then we've got no dice. People tend to wring their necks even at minor traffic accidents, because our necks are relatively thin and the force is applied at the furthest end of the lever, where our heavy brainbox sits.

Not so for dogs. Before we got our dirty mitts on them, 100 pound wolves would latch on to elk and moose ten times their weight, just to pull them down kicking and screaming. This necessitates an extremely muscular neck with strong bone structure. There was significant evolutionary pressure to make the neck, with it's muscle and vertebrae, withstand exactly the kind of forces we're talking about.

That structure exists in every dog today. Yes, even pugs, even if it's significantly scaled down. You can easily confirm this for yourself by looking at any basic diagram of a dog's anatomy. Yes, even pugs specifically.