I am sorry, but hip dysplasia cannot be diagnosed without x-ray. Might your puppy have had some injury due to being thrown out of a car window? Sure. But it seems like he is moving around ok and playing and jumping and using it.
I would not do forced running or jogging on hard serfaces or force the dog to jump up or jump over things, but let the puppy do what the puppy wants to do. You can have the hips prelims done as early as four months I think, but I would probably wait for 8 or 12 months. If the dog is dysplastic, it is not the end of the world, most dysplastic dogs are not crippled, and many manage it without ever showing any symptoms.
As for whether or not your dog is mixed, and what with, my best guess would be yes, and could be anything. But what is important is that the pup is adorable, has plenty of play drive, and if you start working with and training your puppy now, you can do just about anything with him that you want to do.
Thanks for rescuing this pup and giving him a good home.
Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.