Hello! You've gotten some good advice here already
Also keep in mind that all gliders have different personalities. My Thor is a crabber and reacted to being adopted the same as your little guy, as did my Fionn, too. They're just the nervous type! It takes more patience and work with those little guys, but is also more rewarding when you see progress.
I would add to the good advice you've gotten so far these couple of things:
I've learned some gliders like to stay in the cage (like sentries, to protect the pouch). Just remember that when you do playtime, and let the little guy come out if and when he is ready. I used to tuck the pouch inside my shirt, so Fionn would work up the nerve to come out and would be directly on me for that, and then when Fionn had enough playtime (after about five minutes lol) he would scurry back into the pouch, under my shirt. I liked that because I became the safe spot
I wouldn't force him out and eventually play time got longer and he would also spend more time climbing on me.
For both Thor and Fionn, they would (and Thor still does three years later) hide in the corner or behind the wheel. So for hand held treats, like yogurt drops, I would move very slowly, open the cage door, and hold the treat a few inches from the scared little guy. Then, hold still. Prepare to be there for a while at first! Then , you'll see, slowly, the glider will creep forward to get that yogurt drop. Hold perfectly still! Oh, and if your guy is like Fionn, he may snatch that drop fast like lightning and run away. But that's good! This will build trust and he'll eventually come to you quicker and with more confidence. Beware though! My Fionn has bad aim and still occasionally nips my finger when he snatches the treat lol!
So, just be patient. Remember he's scared. You're teaching him to trust you so go slow and try to read his signals. An open environment pouch may help, like Leela suggested, and a friend may help as well, like TJones said. Like BYKChainsaw said do bonding in a small room (or I like the tent), but don't force him out, and hold his treats close enough to him that he can work up the nerve to come to you and get them. Continue to talk sweetly to him, and remember, some gliders are crabbers. Thor just crabbed at me yesterday when I took the pouch out to say hello for a minute in the morning, but he was happy when he saw me and I gave him a treat. In time, your little guy will trust you and love you for your patience.