I'm probably going to talk a lot, so buckle in.
Fake plants: With a veiled chameleon, I just would not recommend them, especially due to the fact you've already caught your little baby attempting to munch on them. If they're plastic, it is exceedingly dangerous for them to eat and swallow this fake plant. Rather than putting the fake plants inside the enclosure, you might want to consider affixing them to the outside of the cage, so the chameleon still feels like it's behind some brush. It's a fairly popular technique here.
This is my own enclosure as an example.
The soil: If you're not doing a bioactive set up, soil is actually not great in general. It just gets wet, warm, and a great place for bacteria to multiply. It's very difficult to keep sanitary with a chameleon's required morning and evening misting sessions. Dealing with the water is the TRICKIEST part of owning a chameleon, in my opinion.
The fact he's eating it fairly regularly is indeed a cause for concern. I would get rid of it altogether, and stick to spot cleaning the floor and/or plant surfaces as soon as you notice they've used the bathroom. It concerns me you mentioned trying to get the chips out of their mouth during eating. It is very easy to damage their tongues, and their bones are very thin and brittle, so some serious damage could come from this practice. There has been occurrences where feeding tongues damage their poor tongues, either getting stuck or the owner "pulling back"/yanking on reflex to the sensation of movement through the tongs.
The best way to avoid your little baby eating dirt and chips is complete removal of the soil. I'd also recommend getting a little feeder cup to put your insects in, if you're scared of touching them with your hands. You can use the tongs to put them into the cup, and then offer the cup to the chameleon. It can be a great bonding exercise too. I use these bird feeders:
https://www.amazon.com/dp/B004LOEJQW?ref=ppx_yo2ov_dt_b_fed_asin_title
Coughing: This really worries me. A chameleon, especially a fragile little baby, shouldn't be coughing or making any sound like that. Is your baby's head pointed upward when you observe the yawning? The coughing and gaping you describe sound very much like a respiratory infection which would require vet intervention. A chameleon, like most reptiles, will try its best to hide symptoms when they know they're being observed. If the baby closes their mouth soon after you glance them, it's possible this is what's happening. If it's not a cough, is it possible that something near or inside his cage is upsetting him? They can get pretty riled up by their own reflections sometimes. They will let out a big hiss as a means of self defense.
Yawning: If you observe this behavior while the baby's under the heat lamp, it's possible he's just self regulating his heat. Another possibility is that it is too warm, which brings me to the other point.
Day & Night Temps: For the daytime temps, for a baby, you'll want mid 70s for the ambient temperature and 80 for the basking. An adult male will bask at around 85. daytime temps can dip to the 60s and it's just fine. If it ever gets to be in the 50s, you can purchase a ceramic heat bulb. These do not emit light and so they won't interrupt the needed day/night cycle for the chameleon.
Feeding: While it's true that veiled chameleons eat plant leaves, they are largely insectivores and we don't offer them vegetables as part of their diet. Instead, we offer the vegetables to the bugs. This is called gutloading. It's a heavy requirement. This ensures the buggies are extra nutritious for our chameleons. I've attached some very helpful feeding guides:
I am once again linking Neptune the Chameleon's gutload ice cube youtube video:
www.youtube.com/watch?v=NKtj5N6SnG8
These can keep in your freezer for up to six months. I will grab my insects the night prior, adding them to the feeder cup I linked from before, and shave off a piece of the gutload ice cube in the cup for them to munch on while I sleep. It's to be noted that insects like wax worms, silkworms, and hornworms aren't gutloaded in this way. Hornworms and silkworms will often come with their food in their cup. This is mostly for your roaches and your crickets. Commercially offered gel cubes don't do much to add to your insect's nutrition, only keeps your bugs hydrated. There are good commercial gutloads, however, listed at the bottom of the second image.
Variety is key to a chameleons diet. I shop at dubiaroaches.com and they have a pretty good selection for pretty reasonable prices.
Sadly, pet stores don't operate so much in the interest of the animal so much as an interest in making sales, especially the impulsive purchases. They will lead you astray with misinformation. Is it possible you could share an image of the chameleon and their enclosure, including the lights? I am afraid you might not have the proper UVB since it's likely they sold you a color night time bulb.
I would really recommend you watch Neptune the Chameleon on youtube. She discusses a ton of incredibly helpful as well as niche chameleon care topics. This video is basically a required watch for new or learning veiled chameleon owners:
I'd really recommend you fill this out too, so we can set you on the right track!
Chameleon Info:
- Your Chameleon - The species, sex, and age of your chameleon. How long has it been in your care?
- Handling - How often do you handle your chameleon?
- Feeding - What are you feeding your cham? What amount? What is the schedule? How are you gut-loading your feeders?
- Supplements - What brand and type of calcium and vitamin products are you dusting your feeders with and what is the schedule?
- Watering - What kind of watering technique do you use? How often and how long to you mist? Do you see your chameleon drinking?
- Fecal Description - Briefly note colors and consistency from recent droppings. Has this chameleon ever been tested for parasites?
- History - Any previous information about your cham that might be useful to others when trying to help you.
Cage Info:
- Cage Type - Describe your cage (Glass, Screen, Combo?) What are the dimensions?
- Lighting - What brand, model, and types of lighting are you using? What is your daily lighting schedule?
- Temperature - What temp range have you created (cage floor to basking spot)? Lowest overnight temp? How do you measure these temps?
- Humidity - What are your humidity levels? How are you creating and maintaining these levels? What do you use to measure humidity?
- Plants - Are you using live plants? If so, what kind?
- Placement - Where is your cage located? Is it near any fans, air vents, or high traffic areas? At what height is the top of the cage relative to your room floor?
- Location - Where are you geographically located?