Maybe try not inhaling. Just in the mouth and out the nose or mouth, whatever pleases? I've come to understand that vaping PG and VG basically coats your lungs, making it more difficult to breathe. Both are processable by your body, but there is still a coating in your lungs even if the juice is 0mg nicotine. It will still coat the lungs. Just an idea. Good luck.
Just wanted to post a follow up update, in case someone somewhere out-there is having a similar issue...
So it seemed that the inhalation of the vapor was causing all the issues for me. I had to find a way to stop vaping (and of course, not go back to analogs in the process). I loaded up with 0mg nicotine juice, and went with the stage 2 nicotine patch and limited myself to mouth/nose hits only as earthbot suggested. It's day 5 now, and I feel much much better (upper back soreness / fatigue / throat clearing all disappeared). To be quite honest, I'm really starting to get into the habit of mouth/nose only vaping.
I don't want to deter anyone from vaping, as it did successfully get me off the analogs which at times I thought I would never be able to do. The all day inhalation of vapor, for me anyway, seemed to be doing a number on me. It may be a sensitivity, inhale method, the juice, the blend, the amount of water --- it's hard to say, but after feeling like crap for almost a year, I'm just glad to be better and don't want to experiment further to find out. The good news is that I'm on my way to do away with nicotine, yet still found a way to enjoy vaping without further issue. Also, I want to note that if you have any vaping linked symptoms similar to mine, the issues are nearly all gone in one day's time once stopped.