Maybe now isn't the right time to get a second cat. He might be afraid of it or try to be dominant. It's wait until he gets used to his new home.
I'm sure he'll feel better. Just talk to him nicely and give him good food (small pieces of raw meat) from time to time. Be near him and talk quietly and gently while he eats, but don't touch him. Just be a few steps away from him. He'll understand you give him food and you're good to him. When you get up ask him if he slept well... Just like to a child who understands but can't answer.
It'll take time but he'll be OK.
And btw cats can scratch you in play. Their instinct is strong and they may forget it's just a game. It doesn't mean he's aggressive, it's just what cats do. :-)