Hi and welcome to the forum
Remhomed or Rescued gliders bond a little differently sometimes. I have a new rescue 2 yr old female who has an issue with skin, and a 4 yr old male rescue who had an issue with skin. This isn't your typical biting, this is almost a fear of skin at least in my experience.
With my male I would let him go into my sweatshirt sleeve ( He would follow my female in there ) Then he would have a brief panic attack, crab a little and scrape his teeth on me or slap my arm with his hand. Both hurt and are startling, then I'd offer him a pouch to go in which he would promptly dive into. I never forced him into my sweatshirt it was always his choice, and his choice to leave it.
My head is one of Simon and Nicky's favorite place to be. I will keep my hood up for the next couple weeks with Nicky and then let it stay down. They both look over the front to sniff my face and neither have scrapped or bitten my face. It gives them a chance to check you out without you "watching" them or looking at them directly which can make them a little braver and less likely to bite or scrape your face. My two gliders with skin issues seem to have a low level of Confidence in themselves.
Looking at them or watching them intently intimidates them, like you are fixen to have them for lunch. Try not to focus all your attention on him when you have him out for tent time or bathroom time, sort of ignore him without ignoring him. Read a book or get on your cell phone, don't be so interested in him all the time and what he is doing when he is on you. It will allow him to explore you more on his terms. When you kind of "ignore" them it also makes them a little more curious about you and why your not trying to pet him or see what he is up to...
Both of my gliders with this issue are on the larger size as far as weight goes, they don't have sure footing on bare skin like a lighter glider has and they prefer walking on clothing because they can get a better grip and don't feel like they will fall. It's kind of funny but with my male it's like he is afraid of hurting me with his nails, and would avoid my arms if wore a tank top, as soon as I put my sweatshirt on he'd march down my arm like he owned it.
Don't expect him to go for your skin just cover exposed skin wear socks, long sleeves, pants hoodie etc... and try not to panic when he tries to check out your face, just bow your head slowly if he is to close to skin and he will go to the back of the head where it's higher. It's passive way to move him without scaring him or reaching for him.
After a couple weeks of head to toe clothes and sweating my a$$ off, I started bra training with Simon, I would put him in a small pouch and tuck him and the pouch in my bra. Leela his cage mate free roams on me and joins him in the pouch then will leave him for her fav spot in my sweatshirt. When ever the pouch would skootch down and he'd wake up with his head in direct contact with my skin he would scrape his teeth on me until I adjusted the pouch for him and he'd go back to sleep. Eventually they start to understand that you "get it" and are trying to help him.
Over time Simon has gotten over his skin issue and doesn't scrape his teeth, crab, or slap me anymore, He is ok on my bare skin, in my sweatshirt with out a pouch. Still if he is in my bra he prefers to be in a pouch but he will go in without one occasionally now.
Nicky one of my new rescues, displays a lot of the same behavior Simon did. I too wear a hooded sweatshirt with the hood up.
NOT in fear of her biting or scraping her teeth, but to respect the fact that skin scares her.
I did however miss the fact that my left sleeve has a hole in it... the hole did not escape her attention though
she was walking down my arm and instantly crabbed and scrapped her teeth on my skin through the hole. I covered the hole and she went on her merry way. Honestly it's like they don't understand what skin is, and why you don't have fur.
It will take time and maybe a few owies for you, but it can be over come. I've had Simon since October, it took me until around March ( 5 months ) until he was over the skin issue and that wasn't his only behavioral issue. He also over grooms, and was pouch protective for a couple months. The over grooming is still an issue for him even though he is no longer alone, has an enormous cage ( 2 brisbane cages side by side ) and plenty of toys and a wheel. At this point the only thing I can figure is over grooming for Simon is a habitual learned behavior he just can't stop.
I don't know if any of this will help you and your glider, but try to give it some time. And try to gradually allow your hoodie to be left down. Then gradually no socks and so on..
Also please consider getting him neutered if he is intact, that might help some of it. And get him a cage mate if he doesn't already have one. A cage mate can be a valuable asset in teaching him new glider skills and to trust you.