i think just expounding on some of those things would be good. Also, giving him a personality type might help all of the quirks and flaws and good things go together a bit better.
Goddamnit I was almost finished and then my laptop decided to shut down….. So here I go again.
Specify what kind of thin he is, what people think when they see him, the why? if you will. Is he the awkward-teen boy-getting-used-to-his-body-thin or not-eating-well-thin or something-else-thin?
Personality type: elaborate on the how? a bit. What kind of people person is he? Does he party a lot or is just going out for casual lunch more his style? What does he look for in plausible friends and other people? What type of humour does he have? maybe give an example of a good/bad joke. What kind of stressed does he get? Lock-myself-in-my-room-stressed or not-sleeping-stressed?
More hobbies might be a good idea. It doesn't have to be something he's good at.
Maybe some more talents as well which don't have to be things he likes doing.
Elaborate on why his flaws are flaws. Nothing is a flaw purely on its own. Write down how it manifests and affect his life and those around him.
Good motivations.
He doesn't have any small or big mannerisms? Nothing like scratching his nose when bored or cackling like a madman when sleep-deprived? If he does have mannerisms, however, be as specific as you can.
Oh dear, the first two sentences of the background are running off to the right.
That's all I could find. Hopefully, you can use it.