What you describe sounds complex, but for the vertigo part, check out BPPV (benign paroxysmal positional vertigo). If you have seen an ENT, they've probably covered this base, but even though it's the most common cause of vertigo-induced trips to the ER, my ER doc didn't cover it. It was two weeks before I saw an ENT who basically fixed it with the Epley maneuver. "Basically fixed" because I still have some lingering (and annoying) effects that echo some of the other symptoms you describe. BPPV is unique in my experience of medicine in that it has a simple test (Dixie-Hallpike maneuver), and an easy fix.
The other thing that comes to mind is Ménière’s disease, a disease affecting the pressures of the inner ear. It's probably also considered if you've seen an ENT. A friend worked on his Ménière’s with diet (low salt, low glycemic index foods), and diuretics, but what is helping now is allergy shots. His ENT noticed that there was a seasonal component to his symptoms and sent him to an allergist. (The first allergist he went to did testing but found nothing; the next allergist found plenty of reactions and hit on an effective treatment.) Actually, his symptoms sound quite similar to yours. The Mayo clinic page on Ménière’s mentions various treatment modalities, though not allergy treatment.