Honestly, Delighted, I think you need to take a step back and IGNORE the fact that he doesn't "act like a Doberman" and figure out whether or not you can love him for him and not the standard he is being compared to. Honestly, I don't understand why you would want a Doberman that dislikes strangers right from the get-go. Dobermans aren't Filas, the ones I know are very eager to make new friends but it doesn't mean they stop protecting.
I have the opposite problem that you do; my dog isn't friendly enough. I have a Papillon. Papillons are supposed to be friendly, happy, bombproof little cuddly lap dogs. They make great agility dogs and have decent drive and focus. This is what I liked about Papillons and is the reason I got one.
Well.. My dog is absolute demon spawn - he is sadistic, aggressive/unfriendly to most strangers, hyperactive beyond belief and more aloof than most sighthounds. He doesn't like training, he doesn't like socializing, he doesn't like cuddling or sleeping with me. He hates grooming, he doesn't even like most training despite my constant efforts to make it fun for him. He does like biting people, peeing on things, shrieking like a banshee and shredding every kleenex in the house. He yaps. He whines. He will run and hide in the most obscure places to avoid being given attention. He steals things and throws extremely noisy hissy-fits if someone interrupts his mischief-making.
I came very, very close to rehoming my rotten little dog on several occasions. But, in the end, what worked was just taking away the standard of the "typical Papillon" that I was holding him up to. He will never be a normal Papillon, he will never be the sweet little lap dog that I wanted. However, he's one heck of a neat little dog despite the fact that he's a demon in a Pap suit. He has one heck of a sense of humor, he is an agility marvel even though he has canine ADHD and will never be very good in competition. Even though he wasn't what I had originally hoped for, I love him and I am so glad I have him.
Perhaps you need to accept that your boy might not act the way all your other Dobies have acted. I think you'd both be happier if you could love your dog for what he is, instead of disliking him for what he isn't.
I still stand by my feeling that a seemingly friendly Doberman would step up and protect their owner if necessary. I would take advantage of his outgoing personality and spend more time socializing him and brushing up on his manners (which need some help if he is straining at the leash all the time and pestering complete strangers). Renee's suggestion of getting into therapy work is a great idea. Just do what he will be good at. Dobermans seem so much happier when they have a job to do.
Edit: As a side note... Even the friendliest dogs will protect if necessary. When my parents go out of town, my lovely, friendly Border Collie changes his demeanor completely. The alphas have left the house and I am left without protection, and I think he realizes that and assumes the role of guardian. When my parents are gone, he does not allow strangers to touch him. He doesn't allow strangers to touch me. He won't allow them in the house or even near the house without my consent. Yet, when my parents are home, he is a complete dork and will love on anybody. He knows that if I need protecting, they will do it. I know it's a bit of a long shot but perhaps your boy is extra goofy around strangers because he realizes your bitch will protect you?