This info can also be found on the caresheets on this site. I hope you are in time to help your little guy, but if he is that unresponsive, a vet really is needed asap
Generally chameleons should only be getting d3 every two weeks. And they should have a vitamin like Reptivite every two weeks. Most people switch these two. Vitamin one week, d3 the next, and back to vitamin. All other feedings should be calcium without any d3. He could be dealing with a d3 overdose, or vitamin deficiency. Or honestly, something totally different, but these two things are red flags to me.
I don't have experience in treating either of these issues. And of course that is assuming that is what this is. And I'm not sure either can be fixed at home without a vet, if he is too weak to be eating.
The lighting alone I doubt could be the cause, however it is not ideal. Chameleons need a dark and light cycle, and no lights should be used at night. They actually do well with a dip in temps at night. If where you keep him gets too cold, a ceramic heater would be better. During the day, the heat bulb can remain on and should keep his basking spot at a specific temp, and chameleons can then choose how much heat, by moving closer or away, for temperature regulation as well as helping their digestion.