shivering doesn't always mean cold, sometimes they are just grooming so the pouch looks like they are shivering. 60* isn't to bad for them I live in fla and have my AC on constantly right now it's about 62 in here. They also shiver when they first wake up sometimes, to get the juices going and their body revved up to be active
The rule of thumb is if you are cold they are probably cold, if you are hot they are hot, like a baby. If you still feel it's to cold for him, cut up some anti pill fleece to put in the pouch that will keep them warm without using a heat lamp.
Do you have him in a pocket pet cage? If so, stealth wheels will fit in it, I have a medical foster in a PP cage right now, the cage is on it's side to make more room for the wheel. I think stealth wheels are the only safe wheel that will fit.
http://atticworx.com/1Stealth%20Wheels.htm
they also sell stealth wheels on amazon.
circling the top of the cage is usually a sign of boredom or stress. Try giving him some stimulating toys, easter eggs filled with treats, drinking straws cut up or curled to play with, plastic bracelets, ping pong balls etc... a wheel will also help.
I know of a couple breeders in washington , Dee McBride is awesome
and might can give you some more names so you have more options for reputable breeders.
https://www.facebook.com/dee.mcbride.58
The vitamin supplement from PP is not what you need for the tpg diet. Tpg has it's own supplement specifically made for the tpg diet, you have to order it on their website. The tpg supplement is only used for the tpg diet, each diet uses a different supplement. 180 days worth for one glider of the tpg supplement is $22.00, a years worth for one glider is 44.00. When you get a cage mate those will feed 2 gliders for half of the amount of time suggested for one. So the 1 yr supply will last 6 months for 2 gliders.
https://www.thepetglider.com/glider-supplies-store/sugar-glider-nutrition
Itching, is what it looks like when they groom themselves. Gliders are very proficient in grooming and keeping themselves and their cage mates clean. They sort of spit ( sounds like sneezing ) on their hands and use it to clean their fur by "scratching" they have 2 grooming nails on their back feet to "comb" their fur with.
Over grooming and self harm...
Over grooming can happen for many different reasons. Being a single glider is just one of them and not every single glider will over groom. Normal over grooming is around the head area. Over the eyes, top of the head, back of the head. It just looks like a lil bald patch. Sometimes it's a concern sometimes it's a behavioral thing that never stops. I have one neutered male with 3 cage mates, a decent sized cage, toys, wheel, and good diet that despite all that still over grooms. His gets worse if I change his cage set up to often, environmental stresser for him, so I don't mess with the cage set up as much as I do the other 2 cages.
As I said there are many different reasons a glider will over groom, If your's over grooms you will need to find the source that is causing him to and try to change it if you can. Boredom, add toys, cage to small up grade to a larger cage ( you can remove the shelves in the PP cage to give him more space the shelves are unnecessary so I'd try that first ) Address one thing at a time and give it a couple weeks to see if the over grooming stops, if not try changing the next thing and so on.
Self harm, gliders don't just self mutilate or self harm from being single gliders. That is a myth. Gliders that self mutilate have an injury or illness or some medical reason for the self mutilation. Many gliders do just fine as single gliders given the human can spend some extra time with them and provides stimulating, enriching things in the cage when the human has other things to do.
Cardstock structures, I'm not sure what those are can you post a pic or a link ??