Gliders don't like to be picked up. (Later, he will climb on you). He's terrified! Your like a GIANT monster to him.
For now, talk to him and let him get comfortable with you. When he stops crabbing about that, maybe take his entire sleeping pouch out of the cage and gently hold it. (Have a treat on hand that he really likes), and if he pokes his head out to say hi, offer it to him. If he doesn't, just talk soft and gentle to him for a few minutes and then put him and the pouch back in the cage without opening it and peeking in ect.
Does he lung too? I remember the joeys going through that stage