Sorry to hear about your Cham. Sometimes it's hard to figure out exactly what is wrong especially when it happened so quickly. It's awesome that you're taking him to the vet on Monday. All I can advises is just to make him comfortable and keep him hydrated until Monday and it might be a good idea to move his cage because Black mold is very toxic and is known to cause all types of respiratory problems in humans. Who knows what the effects would be on animals?
Here is a good link to check out Symptoms of Black mold.
http://blackmold.awardspace.com/black-mold-toxic-stachybotrys-mycotoxins.html
Best of luck with your guy. He looks very sweet. Keep us posted about his vet visit.