9yo boy just not right

My step-son turned 9 a month ago, and from the day I met him I have thought he was a little off. I don't really know how to explain it. He is extremely smart more so than other kids we know. His grades are great but he doesn't talk about friends from school and he doesn't ask to go to other kids houses. He lives in another school district and I have introduced him to kids here his age and to watch him when he meets other kids for the first time is so awkward you feel bad for him. He just stands back puts his hands in his pockets and watches them for a long time the first couple of times he meets them even then he is still weird around them for a few months. I have also noticed he has a nervous habits of putting his hands in his pockets ALL THE TIME even when we were taking family pictures, you could tell he was uneasy about it and we had to keep telling him to take his hands out of his pockets. He gets almost straight A's but the kid can't dress himself properly I have to pull out his whole outfit and he comes out with collars rolled in the elastic band of his underwear rolled in on one side bunched up and twisted. Socks are inside out all the time coat falling off half his pant leg tucked in his sock and he just looks like a boofer all the time till I stop him and fix him up. He can tie his shoes but doesn't know how to tighten the laces multiple times I have had to sit him down and say this is how you do this. Just simple life functions the kid lacks. If he gets hurt at all it is  a huge ordeal. If you discipline him he screams like we are beating him and we never have and I can say I don't believe he has at his mothers since she doesn't discipline them at all. His 4yo sister doesn't doesn't react half as bad as he does. He is also very emotional you walk across the room and he hugs you all the time (not that I mind) it just seems weird for his age. There is so much more but I don't have the space any ideas are welcomed.