As an allergy and asthma sufferer, I totally agree that LPR and sinus/allergy/asthma symptoms can be interchangable. You can go on a wild goose chase with GERD/LPR worries, only to find out that your symptoms aren't acid-related.
That said, it's very possible to have a combination of problems--especially if you have a hiatus hernia and reflux symptoms. It is definitely muddy waters, indeed.
Glad to hear you've gotten to the bottom of what's going on. Good luck with getting things feeling better. Allergy issues are mighty hard to deal with as well.
My sinuses are the first to react to pollen, and so far my allergist hasn't been all that successful in solving my problems.
Very best wishes,