Most large and giant breeds of dogs have dominant personalities. Hitting them will have far less of an effect than hitting a smaller breed (where it could take years to recover). Pitties, like rottweiler’s are hardy and cope well with a dominant “leader of the pack” and stern discipline.
In many ways it’s a natural response to lose your temper or grab a dog and chastise it. Grabbing her by the scruff of the neck and showing your disapproval of a certain behavior is not a bad thing. I’m not endorsing hitting a dog by any means.
How long it will take to eliminate the trauma from being hit, all depends on how often and how hard you’ve hit her. Cesar’s “Tsch!” sound is the most effective form of redirection, along with a touch with three fingers which represents a “claw”/”bite” between the neck and shoulder or hip area.
Recovery of nose smacking
To start it would be best to not smack her nose again, and make a habit of several times throughout the day, slowly approaching the side of her head (not her face) with the back of your hand to gently stroke the side of her head and give her gentle verbal praise whilst petting her.
It’s a matter of regaining her trust (in terms of when your hand approaches her face). You need to convince her that your approaching hand means a reward and nothing bad happening.
When it comes to a small dog, there is a limit to how many food rewards you can give her in one day. If she has a treat she is crazy for, put the treat in your left hand (for argument’s sake) as you do the stroking exercise with your right hand and verbally praise her, you can slowly raise your left hand up in front of her so she eventually will look down and sniff and take it from her hand.
Praise her verbally when she takes the treat “that’s a good girl”. Do this every second or third time you are doing the stroking exercise, it will reinforce the positive nature of the stroke and verbal praise.
Being scared of strangers
Many dogs react to a person putting their hand out. In this case, it would, most likely, be exacerbated by smacking the dogs nose as punishment. It is always better to offer the back of the hand in the direction of a strange dog and allow the dog to come to you and sniff. I would suggest, you proactively prevent people from attempting to pat her.
You can do this by using your arm to prevent their arms from moving too close and suggest to them: look my dog is very timid, perhaps you can put your hand like this and show them how to approach your dog in a non threatening manner.
Scared of other dogs
Socializing in a dog park is always a good way to help your dog interact with other dogs. This is vital for younger and/or timid dogs to begin with, as a dog park or doggie day care is more controlled, the owners are aware of any anti-social behavior within their dog community and the dogs are supervised accordingly.
Whereas an off leash area for dogs can be a bit chaotic for a small, young dog, and you don’t want her to have any bad experiences that will set her back.
Barking in small dogs is a really common problem. Partly due to the fact, little dogs are continually needing to reassert their authority, due to their lack of size.
I suggest having a look at the post here How to prevent my dog from barking too much for some advice.