All dogs are not the same. Dominance is not an individual trait, there are no 'dominant' dogs, it is an ASYMMETRICAL RELATIONSHIP: in a relationship a dog can be stronger or weaker.
I have bad news: there is no aggression scale. Dogs do not go through all these stages before attacking and before biting. The graphics are eye-catching, I know, but they can be really misleading if we want to understand aggression in dogs.
The belly-up posture, with the dog standing still, is described as passive submission. During play, however, it may be the stronger dog that goes belly-up
For many years I have heard trainers repeat that "you must teach the dog not to pull on the leash".
One statement, two mistakes.
"In canids and dogs, urination is also part of social communication, representing both an olfactory and a visual signal (posture)."
"The bow is one of the most misunderstood behaviors in canine communication."
We have learned that in order to train a dog we must use positive reinforcement: a dog's behavior leads to a positive consequence = the dog repeats the behavior.
A dog can be stressed by the person holding the leash, or by something that is in the environment: dogs, people, objects, noises, smells...
Dogs do not pull on a leash. Pulling is not a behaviour, it is the consequence of a behaviour.