How can I make my chin happier

Hi there,
I have a chinchilla that my family adopted and gave to me last Christmas. He lived his first year of life exclusively in his cage and with no dust baths or hay. Of course I've brought him to a vet and corrected his diet and I give him his regular baths. He gets a few hours of time outside his cage usually from 8pm to 2am. He's still very shy and prefers not to be touched. I know that because he wasn't really socialized as a young chin and that my care is the most extensive he's really gotten in his life. Sometimes he can be very moody (although he has a very stand offish personality to start) and he often has no interest in playing or doing much of anything. I feel bad because he gets his time out of his cage and has free range in my chin-proofed apartment but I have a hard time getting him to interact with me. He knows me and my boyfriend and allows us to hold him but only briefly and I always make sure to give him a healthy treat afterwards. He seems almost bored although he does play almost like a game of tag with us when we're trying to sleep. I just want to make sure he's the happiest he can be