If he has been desexed, he may never lift his leg to pee, whereas he may start doing it as he gets a bit older. They are all different. We have two boxers from the same litter both male, one squats, the other one lifts a leg.
As for the barking when you leave, he is trying to get the attention he craves, and knowing that the other people who live with you are going to eventually "give up" too his barking. That would be why he is relentless. Make sure you leave him with a kong, to try and keep his mind active and only when he is quiet in his crate to pay him any attention what so ever.
As for being timid and a little anti social, have you been socializing him since you got him? If he isn't getting any better over this amount of time maybe seek some obedience classes, where he will have to interact with other dogs and people. The traffic could be a cause of a problem later on(if he got out and ran onto the road) I suggest you be as calm and in control with your body language as possible, try not to put pressure on the lead. If you ignore the problem, he should hopefully feed off your energy. Is there anyone in your neighbourhood with a dog who is very calm on a walk, ask if you can join them, or borrow their dog for walks. He may need the confidence from a bigger pack. Also, I have found with dogs that have anxiety, put yourself inbetween the dog and the problem. So walk the dog on your other side.
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