I wouldn't count on the veiled eating vegetables. Mine hasn't eaten any in a long time, which is why it's important give the feeders a variety of different foods. Commercial gutloads are super good for this.
What do you mean by upgrade? If you want retain humidity better you can coat the cage in plastic and for plants I suggest getting something like Dragon Strand ledges. I've heard they work really well.
Arcadia makes really good bulbs and for basking normal bulbs are fine. You might have try a few different wattages to get to optimal basking temperature. For plant lights, I don't think you'll need an extra lamp for them unless your cage has loads of plants or if the light doesn't reach all the...
Which product are you talking about? Amazon is pretty good place to find all sorts of reptile equipment. You could also look through the site sponsors.
Looks like mouth rot to me but I'm not an expert on that. I suggest you take him to the vet and fill out the help form in my signature, if you haven't already.
You should set up a drainage layer if you are using a substrate instead of a bare bottom. Plastic egg crate works super well for drainage. Just put this on the bottom and then some carbon fiber window screen mesh on top of it and then just add your substrate. That way all of the water will drain...
Mealworms are a big no for chams. Feed him crickets instead. You could also fill out the help form. https://www.chameleonforums.com/threads/how-to-ask-for-help.66/