I hope you feel better soon! I can't imagine that a sensitivity would stick around this long if you completely stopped vaping.
My go to "Sore throat" drink when starting vaping was chamomile tea with lemon and honey. The honey kind of coats your throat, the lemon clears up mucus and the chamomile tea helped with general irritability. I'm drinking some right now as a matter of fact (not because I have to, just some general annoyance) and I continue to maintain that chamomile tea is more calming than any OTC product has the right to be.
I also think the Zenith is a really good flavor tank, but since you've had no joy in that department, I kind of wouldn't recommend getting one until you get all this illness stuff sorted out, you may well not need it if you are able to get back to vaping in a way that makes more sense for you. It is a nice flavor tank, it is also (in my opinion) not at all like vaping a direct lung setup.
I hope you feel better soon.
Anna