Yes definitely take out the substrate, especially with such a little baby. They can eat it and become impacted. Use paper towels or nothing at all. It is also much easier to clean and keep him healthy.
No sometimes they start doing it when they are older. Get a schefflera, sometimes mistakenly called a "money tree" but it's not, it's an umbrella tree.
I have heard they can be toxic? But I have one with my panther because he doesn't eat foliage. So if your panther doesn't eat the plants then I would say it's okay.
well, personally, I hate coiled bulbs. But that fixture is actually supposed to house one UVB bulb and one heat bulb if i'm correct, so you may actually be giving him too much UVB.
Actually I have heard gular edema can be caused by oversupplementation of vitamin A, as well as swollen eyes. I would not give vitamins for a while, maybe 2 months? Also, are you giving calcium with D3 at all? That could also be causing it.
A vet checkup is always a good idea, Jann does almost monthly checkups on her babies! But if it's only dry skin, which would look like little white patches of skin, mist her a lot with warm water. That should help. Just try not to get it in her face, babies that small could aspirate water...
If I were you I would fill out this form, so we can try to pin point what may be causing it. Skipping one day of multivitamins won't be causing it, but by the way you worded it it sounds like you are giving them to her weekly? Also now that her eye is puffy too, it could be a more serious...
If she is a veiled or a panther, here is a great blog by my friend with everything you will need to know: https://www.chameleonforums.com/blogs/jannb/325-info-new-keepers-young-veiled-panther-chameleons.html