I would say if you're doing something and it is decreasing your tinnitus then there's a very good chance those two things are related. Allergies can surely be a culprit of T. Keep up with the Flonase if it's working for you and maybe see an ENT or allergist. Summer can be a bad time for people with allergies.
Even if it's not your allergies causing the T is a really good sign it's going away at all. Try and reduce your anxiety and stress as much as possible and try to not think about T. It has a funny way of creeping back when we're stressed or at least seeming worse than it is. Keep positive that you've had a reduction of symptoms at all. That's very very promising. Wish you the best and hope your T stays away forever!