Great model, but the hair is a big issue. I went to try to fix it on my own and reached a result I was happy with. I don't make models, so you're certainly better than I am. However, here is some information others might find helpful.
I see that you wanted to add some form of hair physics, and I appreciate that. However, this results in the hair (and the model) freaking out.
I went ahead and used Unity to remove the physics (all rigidbodies, colliders, and the animator) from the hair. Sure, the hair didn't collide with the body, but at least it didn't freak out.
I don't really have a solution outside of that. I did play around quite a bit, and the only thing that might help is to remove physics around the neck area. There really isn't any need for the hair to have any collision above, or even at, the shoulders.