Elvis is still pretty sick. He sleeps all the time, not wanting to eat or drink. I'm having to force feed him, using a combination of Oxbow's Critical Care (thanks a million, Sassy) and Felovite. I'm also giving about 1/2 of a CC of water by syringe a few times a day to ward off dehydration. He took it a bit better this morning, but still has no interest at all. And after the second night, there have been no poos.
The mucous look to be coming from his anus, which REALLY scares me. There is a cavity that needs to be closed off when a chin is neutered that leads to his abdomen ... I'm afraid this wasn't done or has come open and caused all of this. The antibiotic just doesn't seem to be helping. He literally just sits and lets me hold him, which is so rare for Elvis. I took some pics, so you all could see what I was dealing with.
I also found out that I was misled -- this was the vet's first chinchilla neuter.

Had I known that, this never would've happened. The receptionist AND the techs told me he'd done many of them, in addition to guinea pigs, etc.
I've spoken to an exotics vet in the closest big city and I may take him in to her on Monday. She was willing to discuss him with me over the phone and offer some advice on what to test for, etc. I was very impressed -- she actually seemed to care.
At this point, I'm looking for advice and I guess a little support. He's my first chin and my baby ... I'm so afraid I'm going to lose him.