Ok. It's definitely quite a warm cage, so that would explain the gaping.
You certainly want to get that heat mat out of there right away. Heat mats don't work well for chams, since chams perceive light sources as sources of heat, and won't benefit much from underfloor heating. What are you using as a basking light?
Also, and this is important, inasmuch as they need a warm spot to bask, they also need a cooler spot to escape that heat. An ambient temp of 30C in the cage is a bit too warm.
You would probably be better off with ambient temps ranging from a cool side (usually at the bottom of the cage) of about 22C up to about 28C at the top end, and then have a basking spot that is between 30C and 35C.
Then at night you would want the ambient temps to drop to about 20-22C in summer - in winter you could let it drop to as low as about 15C.
It's important that you allow chameleons a period to cool down. A heat pad that is on 24hrs a day isn't going to do that.
Live plants are provide a major boost to the humidity levels in the cage, and also help stabilise the humidity levels in the cage. Also Veileds can be voracious eaters of foliage, and they could easily do harm to themselves by eating fake plastic plants. Study the list of safe plants on this site and try to get some of them into your cage.
You're going to have a flood of posts telling you that a waterfall is not a good idea in a chameleon cage.
Have you seen him drinking from it? In this case, you will have to ensure that you keep it spotlessly clean. Chameleons have been known to use standing pools of water as a good place for their droppings, and also feeder insects drown in the water quite often. All this just contributes to massive bacterial growth, and you don't want your chameleon drinking from that...
Greenish fecal matter is a bit odd: you should be seeing two brownish/blackish pellets, followed by one bright white pellet that is the urates. Discoloured (usually yellow) urates are an indication of dehydration.
You need to consider the role of Vitamin D3 and Vitamin A in your supplementing and gutloading. I'm sure Kinyonga will make a post to this thread to clarify it all (if not, do a search through her posts to see what she has said before on this topic).
In the meantime, read everything you can at these two sites to learn more about chameleon keeping:
http://www.chameleonnews.com
http://www.chameleonsdish.com