I would be wary of the teeth grinding, mine do that as a warning. It might mean you're going a bit over what he finds comfortable.
If you've only had him for a few days don't expect a miracle. Mine are still becoming more domestic and I've had them two years. I would say 3-6 months for real comfortable relationship between you and your PD. Just spend lots of time with them, not even playing just around them so they get used to you.