His small frame and face didn't develop overnight. I agree he looks like he has a condition and probably does have some mild genetic anomaly that doesn't matter to his health but causes certain visible displays that we're all picking up on but I don't think it's adult onset tourrettes. It could also just be an unfornate look and overcompensating with the profound desire to be loved by a work-a-holic father who raised everyone else's son disguised by an insane cheerfulness that we all know deep down is masking a man about to snap and kill us all so he'll finally feel visible.