I'd bet you have a neutered male with an irregular scar. I've seen it before.
People who will do neuters by methods that most of us would not approve of are not caring or knowledgeable enough to check that there are actually two testicles in the pom when they cut it or tie it off. If a glider is a criptorchid (meaning only one or no testicles have descended into the pom), then that testicle(s) would NOT be removed in the poorly done neuter process. Criptorchid gliders are sterile, but they DO get large bald spots and have a slightly musky intact male scent (because they still have the one or both testicles). I have one in my home right now.
Many male gliders open up their neuter site after neutering just to remove the pressure of stitches or glue. This is perfectly normal for them to do and does not mean they are self mutilators. Most of them heal a little better than this one because most of them are neutered more responsibly. But, I have a few male gliders who have neuter scars that look similar to this.
This would account for your scar and for your bald spot. ;)
Neutered males are my FAVORITE!!!! And, you don't have to worry about your other one being pregnant. If he was neutered, then he can't get her pregnant. The only options you have are neutered male, hermaphrodite or female. Either way - no testicles = no baby.