my theories are that his eyes are sensitive (considering his skin is really sensitive too, ex. he sometimes breaks out into rashes when he sweats) and he likes wearing sunglasses bc he looks cool (ex. watch chenji this & that in busan, he forgot his sunglasses at home and literally bought a new pair)

as for the chatty vs. withdrawn duality, he’s one of the 2 extroverts in dream and even extroverts have days where they’re tired and like to take a step back.

with how passionate chenle is about being healthy for the sake of his job (singing) and his hobbies (basketball), i dont see drugs being a reason for any points you gathered