He sounds just really afraid. I have one baby we bought from a great breeder, who was like that. We let him settle in for a couple of weeks, no handling just feeding/cleaning. Then we started handling him every day, sometimes several times a day, just for 5 minutes or so each time, unless he had eaten. We have gradually increased the time we keep him out to about 10-15 minutes, and decreased the number of times. We only take him out once every day or so now, but it's just a few minutes before he is moving around our hands checking things out. That was 5 weeks ago, now he is one of the nicer babies....lol. Sometimes it just takes time. He's probably not coming out because even a 20L is big for a baby. I keep my babies in 6qt sterilite tubs with locking lids. They like the small space and seem to do better. If you want to keep him in the 20L, that's not a problem. Like I said, I'd give him some fake vines and greenery to provide him with some cover. That way if he wants to come out, he won't feel so exposed. Remember, babies are small and feel vulnerable.