He is becoming more self-aware and wants to keep a distance,

 

thus his long face, to repel you.

Any attempt to get close is viewed as wanting to subsume him again, (as what used to be.)

Treat him as an equal. Respect him as an individual. Give him space. Don't talk down on him. Hard to do for Chinese parents.

Remind him that happiness is a choice; one can always find things to be unhappy about if he wants to. Do not blame others. Be responsible for himself. Try to be helpful to others. Count the blessings and be grateful for the good fortune that he has to be alive here and now.

Read the Bible (children's version) and learn some history, because it all started long before he was born.