It looks like the bars of the cage in that picture might be a little dirty. Did he come with that cage? If so, it could probably use a scrub. I rub the inside and outside of mine from time to time with a paper towel wetted with rubbing alcohol. Gliders will pee on the sides of the cage and get the cage messy/smelly. Cleaning it up would probably be nice for him, but also nice for you, because his home will smell better. :]
That's really awesome that you're already planning on getting him a companion. My girls are so much happier now that they are together. I also agree that you should look into getting him neutered.
Does he have a glider-safe wheel? I have a Wodent Wheel right now, and I'm not super happy with it. I want to get my girls the Eco Raptor soon. But if he doesn't already have a wheel, I would suggest getting him one. I bet you it will be his favorite toy. Plus it's really great exercise for him, especially on nights when you can't give him as much time out of the cage for whatever reason.
It's important to keep a 2:1 ratio of calcium to phosphorous in glider diets. Go to the search tap at the top right of this page and search Gliderpedia and the old threads for info about calcium to phosphorous ratios in different foods. Then you can take that into account when you buy produce for him.
It's great that he's not crabbing, letting you hold him in his pouch, and taking food from your hand.. It sounds like you've got a real sweetie. I'm sure that with time, as he adjusts to his new surroundings, he will become more interested in interacting with you. Might I suggest letting him sleep in your shirt/bra? Mine just crawl in my shirt and sleep all day, but if he's not comfortable with that yet, you could let him sleep on you in a bonding pouch or in his sleeping pouch. That will let him get used to your scent while he's all snuggled up, sleeping and feeling safe.
Good luck with the little guy! He's sure a cutie!