What is wrong with my BOMBAY KITTEN?

I would take him back to the vet. It sounds like the poor thing could be dehydrated and need some fluids. He could also need a round of antibiotics as the eye infection could be a symptom of another more serious infection. Listless cats are sick cats. It sounds like you paid a lot of money for him, so don't take any chances with his health. Get him to the vet. You'll be glad you did. Good luck.