I think that Dauphins attitude towards his horse was pride, yes pride in a way that someone has pride for his sports car, in the same way Dauphin was saying his horse is like the Pegasus . 
The reaction of the Constable is that he is tired of the prince's arrogance considering how long he knew him.  Form what I've seen of Dauphin, he does not deserve their respect, when you ask me if they respect the Dauphin.
 Now, in reference to whether or not Pistol speaks french, well, you will know when you read this quote. "Say’st thou me so? Is that a ton of moys?—Come hither, boy. Ask me this slave in French what is his name."  Yes I think not, you see Pistol captured a French gentleman but he could not communicate with the French man.  So he called "The Boy" over who could speak french, thus using the boy to tell his captor, to prepare to die.  Hearing this the French man offered a some of money in exchange for his life, which had profound effect on Pistol.  When Pistol heard this, he agreed to the French man's statement.
 Really, comparing King Henry to Pistol in how they treated their prisoners, to my surprise, it seems that pistol was more merciful.