The winters around here have been so slight that more and more mold and bacteria and pollen have been multiplying causing sinus issues in people who usually don't have issues and reaping havoc on us that have always had issues. I have had sinus issues my whole life and after multiple sinus infections and sinus surgery to open up blocked cavities I was sent to an allergist....kiddingly I asking if he had a box of test serums for St. Mary's....he was dead serious and said he did. He said that the way the stuff in the county blooms (spring or fall) creates an extreme condition in the environment like nothing he has ever seen or read about before that will most defiantly cause sinus/allergic issues to anyone who spends time in the county. I also kiddingly asking if he could test to see if I was allergic to my BF....he got mad at that one and said I would be surprise how many people are allergic or have a reaction to their significant other. The sloughed off skin cells we deposit all around all day and the natural odor we all have (that is different to everyone) can cause sinus/allergic reactions to people.
With all that being said, what I believe is happening with you is the sinus mucus is up in your cavities and may be partially blocked from past sinus issues that the netti pot isn't able to flush out which is causing pressure in your sinuses and ears causing the dizziness and your other symptoms. I also think the netti pot maybe causing the drying out of your outer sinus which can cause inflammation and again the pressure.
Try not using the netti pot but once or twice a week, take Musinex D/DM to get your sinuses to start draining and use a saline spray often during the day. The times you don't us the netti pot try putting HOT (as hot as you can stand) compresses across your face (ear to ear) to cover your cheeks and nose and across your forehead just above your eyebrows. If you can, take Advil or something similar to help bring down the inflammation in your sinuses and ears. If this doesn't work after two weeks (and believe me I am 48 years old and have been dealing with these type of sinus issues in this county my whole life and have done everything I have suggested because of the same symptoms you mentioned) then I suggest you request the CT Scan your ENT recommended....you might have blockages in your sinus cavities or growths in your sinus cavities and/or ears.
Great Post.
Thanks.