Here is a comprehensive list of the safe and toxic foods:
https://sites.google.com/site/oakleysglidersite/safe-and-toxic-foods-list
You're right, this site has such a wealth of information that has been compiled over the years into the Gliderpedia. There are also always good folks here in the forum to help out with specific questions.
Congratulations on your little guy. A couple questions. At 4 years old...has he always been a lone glider? How did you acquire him? If he's a little chunky do you know what diet he was eating before he came to your home? They can get heavy even on a good diet, but many times it is due to poor diets. In that regard, have you gone through the recommended diets and found one that you will be using?
You're already doing a good job, wanting them happy and healthy is key!
You've asked about bonding. I won't go into it at this point, there are some articles here, as well as people who will come along shortly that have their tips in a "copy and paste" format. I find it easier to troubleshoot as it goes along. LOL
Best of luck and glider love!