One: Veiled chams need a basking spot of at least 90F. Your misting schedule also needs to be tweaked. 10 minutes in the morning, and 10 minutes in the afternoon, with a dripper is sufficient. More is asking for a respiratory infection.
Use linear UVB bulbs. 10% is good. Also, Petco has large screen cages for $70 shipped. If you really want to amp up space, you can buy two and connect them.
Also, old bulbs are probably bad. You want a new one, and then replace it once every 6-8 months. Even if the light works, the UVB can...
Anything that comes in a "kit" is generally not the best for a chameleon. I would recommend looking into getting new lighting (a good UVB linear bulb), and getting him hydrated. He also needs gut-loaded crickets (the gel is usually just for moisture, try some carrots for something easy to feed...
When was the last time you changed the uvb light? They generally don't give as much UVB after around 6 months and need replaced. Also, since he's free-range, are you sure he's under the UVB light often enough? From what I've read, it could stem from UVB/vitamin deficiency, to a physical defect...
Too many things could be wrong with the set up, not to mention whatever is going on internally. From the picture, I'd suspect improper lighting as at least part of the issue.
Superworms can climb on the screen like a cricket does (only not so well, they fall more often). Try letting the superworm attach to the screen near him and see if he goes for it. Dubias can be set on a leaf nearby, and if he goes for it, it won't have time to walk off the edge.
Your UVB T5HO should be 10.0 for starters. Basking spot should be 85F-95F, and the bottom part of the cage should be cooler to allow for a heat gradient.
A tip for the hibiscus plant that I've learned through experience (I have one for a tortoise)- They don't need as much sun as you'd think, but they love love love water. My plant only gets direct sun in the morning for about 3-4 hours, after that it's shaded. They get BIG and they grow quickly...