The "loner" thing...probably just his personality. My boy was never really a cuddler either. He clearly doesn't "love" getting pet although he'll stand around and let you do it because he knows you want to. He consistently sleeps either on the other side of the room from the rest of us, or even in a different room.
The growling is probably just play. I wouldn't consider that aggression at this age. Lots of puppies, especially with stronger personalities, don't like being picked up. So he's letting you know that. He doesn't know a different way of saying "I don't like this" so its growling and biting at this point. You just have to teach him that its not acceptable.
I'll tell you that I have a very stable boy, he's extremely aloof, just doesn't like a lot of human contact. He'll greet us like a normal dog and then calms down quickly and goes to get a toy to play with. He knows that our interactions are based around a toy so that's what he does. He's a therapy dog and we go to schools and nursing homes monthly for him to entertain people. He's completely safe in crowds and is much easier to handle than dogs that want to say hello to every single person that walks by. He just does his own thing...
I wouldn't worry about these small things at this age.