@JohnFox,
I will try to answer some of your questions.
I do not know why this happened to me exactly but the ENT said it was probably a virus. It did not happen at night. I have not regained any hearing. My deaf ear reacts to every sound I hear in my good ear. That still happens but is not as extremely painful as it used to be. I can tolerate being in loudish restaurants now (without ear plug) but I am unable to hear conversation there. I still carry earplugs everywhere I go but I don't often use them. I find that exposure to noise over a long period of time is still taxing. The pain is not as sharp, more of an ache or pressure.
When I stopped fearing sound, the hyperacusis got somewhat better. I used to fear all kinds of little sounds. Even though my ear still reacts to these small sounds, I am often able to ignore the physical reaction because I am not focusing on it or fearing it.
Hope this helps you.