Tim, welcome to the forum. There are many of us on this forum that have failed back surgeries. That is where the pain management comes in. I had to take a hard look at the amounts of meds I was taking for pain at one point and made the decision to find another way to reduce the pain meds. Unfortunatly it seems that you are in a difficult point. The data shows that smoking limits the ability of the bones to fuse. I am also an ex smoker but it was a blessing when I made the clean break from it. I agree in the point with your dr that a major step is the smoking. If it interferred with the fusion once it will probably do it again. Who in the right mind or wrong mind would want to go through another fusion surgery? I have had three back surgeries and I would have to be talked very hard into another one. My fusion was a sucsess from the fusion point but the nerve damage is a whole other issue.
Without attacking the smoking issue, the pain meds will only help so far and then they will become the problem. The less you have to rely on them the better. I would encourage you to ask your doctor for help quitting smoking and then look at the option of re-doing the fusion.