The shaking, quivering of the abdomen is common among greys, they just do it.
Your grey is acting territorial about his cage, maybe you need to allow him to come out on his own or entice him out with some sort of treat, or like someone else mentioned you may have to just get him out, bite or no bite so he knows who is boss. My Josey is easy and I can get her out, no problem, she is a very sweet bird.