OK. One month is REALLY young to sell someone a chameleon, but you seem to be off to a pretty good start. Get yourself a timer and put those lights on it. Midnight is way too late to have the lights go off - I try to do 13 on, 11 off in the summer, and then decrease to 12 and 12 during the winter. I'm in Florida, so our days are always longer than yours are up north, but that's a good start. Don't worry about not seeing him eat, drink, or hand feed from you. He's still settling in, and has just had a huge change from the petstore to the mansion that you have for him.
To me the 100 watt seems a bit much, but your temps are good, so as long as you know they are accurate I'd be ok with them. The "yawning" could be him trying to thermoregulate - they will open their mouths to cool off, so that's why it's crucial that you know those temperatures are exact. Does he "yawn" by holding his mouth open for a little while, or is it more like he opens and then immediately closes it?
Finally, I know you just got him, but you're going to want to make sure that you read up on supplimentating your chameleon - you'll need more than just the calcium with D3. However, you've only fed him twice so far, so I'll just mention it for you to research. Read up on the care sheets for more info.
I think you are doing well so far with what you are doing. Give him time to settle in - I know it's tough, but leave him be to explore his strange new world and the humans who are now living with him. Good luck!!!