I foster and work with seriously stressed out dogs.
1) Medication to help the dog calm down so she can think. This is usually not permanent.
2) Find a good trainer to help you. See if your vet can recommend anybody.
3) Yes, I own and use basket nuzzles when working with rehab dogs. I like the Baskerville brand. Look up how to introduce dogs to nuzzles- squeeze cheese is my preferred bribe.
I can tell you that my foster dogs have gone on to have happy lives with their families. No, they don't go to off leash parks and doggy play groups. They do hike, camp, go on car trips, sleep with the kids... it takes time and patience, and a good team.