First off, a glider's anal glands really should never be expressed. It is very dangerous for them and could be the very reason he is still sick. A glider's cloaca is a multi-purpose opening, and squeezing anything into it (as can very easily happen when one expresses the anal glands) can cause infection to spread to multiple organs in the body.
If your glider is truly having multiple issues with anal gland infection, then the glands need to come out. It is a very, very simple surgery for sugar gliders, as the anal glands are not the same as they are in cats or dogs. Furthermore, your glider is not at all too young for surgery.
Please give me a call
806-274-9177.
Also, next time you are at the vet, have your vet give Dr. Walsh a call. He is extremely experienced, has removed anal glands from gliders before, and is the vet I trust with all my special needs gliders.
As an aside - from your picture it does not look like your issue is anal glands, it really looks like your glider has a different issue. Please call me to discuss this.
A glider's anal glands are a bit further back. It is not the best picture, so I could be wrong, but I'm suspecting you have a different issue going on.