You are correct when you say that you recieve the abatement of pain with fermented wine. How that is acheived is directly from the alcohol. Alcohol in any form is a depressant and therefore numbs the pain receptors in the brain. When the nervous system can’t transmit the information correctly to the brain you simply are not aware of the pain. For example; Long before the days of a dentist being able to give an injection of novocain to deaden the pain of having a tooth worked on it was common practice to give the patient a couple of shots of whisky. Net result, the patient felt less pain.
There are however a varity of midicinal benefits from the grape that are highly desirable with or without the presence of alcohol. It is those benefits that provide the midicinal effects that are often spoken of when refering to wine.
One analogy: People have for centuries claimed that a little alcohol would serve to warm you up when you are very cold. The truth is that alcohol actually lowers body temprature. So why is it that people say that feel warmer after consuming alcohol? The facts are that they feel a little less of everything, incliding the cold, and thus think they are warmer.
Respectfully, your brother in Christ,
PS: I do understand back pain as I have lived with it for over 50 years. My back has been injuried so many times that it could be used to teach what not to do to your back.