Fear or nervous based aggression

If you can I would get in contact with Ceser The Dog Whisperer.

look up on youtube for the video of the dog whisperer aka Ceasar Milan look for the episode with Eppie the Staffordshire bull terrier. It was having similar issues as your dog is having and his technique has just about cured the dog. but it will take some time, dogs just dont completely change overnight. you hveto spend time and work with the dog and be consistent.

i cant look this video up without the link because their are too many dogs called eddie that are staffs, unfortunately. thank you