Once percs are happy with a particular spot, they rarely stray far from it for long periods. "Bobbing" in a motionless state is also normal. If the clown is eating well, shows no sign of a parasite or has any appearant breathing problems; it should be fine. Just keep an eye on it for any changes in behavior.
As far as the blenny, it really depends on what type. Some will aggressively defend their territory while others will either ignore intrusions or just give a quick chase. If the blenny is not constantly harassing the clown, they will soon sort things out and establish boundries. In a 65 gal
, there's plenty of room for the fish you have.
How long have you had the clown?