lay on the floor with treats all around you...don't move, don't look at him, don't do anything, and just wait, and see if he will come out, if he starts to eat treats from around you don't move, not until he's done, and if he walks away, get up and leave.
If he doesn't come out for 10-15 minutes, try again another time.
Try and practice some training sessions daily, keep them light and fun! Use a light happy voice, no stern tones.
Training and a calm attitude will help form a close bond, your dog just may be very sensitive to "rough" punishment, which means you have to try and check yourself when you get angry or frustrated..just remember, its not the dogs fault, they don't speak English, and its up to you to teach him a bit of our language, but well enough so he remembers it and finds you a wonderful leader who he has no need to be afraid of.
And like everyone else said, no more harsh NO's, or stares, if he does something wrong, redirect him, make him sit, or tell him to do something, and praise him.