I am so sorry to hear this happened.
As a large dog owner and semi-retired sled dog racer, I would say the pit bull's owner is at fault. The pit bull isn't necessarily people aggressive, but could be. Dogs have a natural instinct to go after prey--and sorry to say, but your goats are on the menu. That doesn't preclude the owner from keeping his dog under control at all times.
I too second that you were perfectly within your right to walk your goats on leash on the road. Now that you had that experience, I would keep a nice bottle of bear pepper spay with you for the purpose of keeping possible dogs from getting at your goats while walking. Yes, I don't think you should have to carry one in a perfect world, but our world is seldom perfect.
As for dog bites -- you did good to give your goat a shot of Pen G. Keep that up. Dog bites are notoriously bad for infection because dogs have enzymes in their mouths that break down tissue. Also, flush the wound out with a syringe filled with a mix of hydrogen peroxide and water. You want the wounds to heal from the inside out. Dog bites, especially big ones, do a lot of damage by trauma (trust me -- first hand experience here!) Your goat is in a lot of pain, so if you can give her bantamine or some other pain meds that are safe for goats, do it. Use ice packs wrapped in a towel on that neck to reduce swelling. I would also talk with your veterinarian about looking at her neck, if you can.
The shaking is due to pain and being shaken up. Pit bulls bite with something like 400 lbs per square inch, which is pretty gnarly. Keep an eye on that doeling. Shock is characterized by a drop in temperature, pale gums/low capillary refill rate, and a fast, thready pulse. If she's showing symptoms, maintain a consistent body core temperature and get her to the veterinarian ASAP. With pit bull bites, there can be internal bleeding.
Good luck! Let me know how it goes.