I feel I have to stress that I am not a doctor, so I can only speak from personal experience, but I understand and share your frustration that most doctors don't even seem to want to try to help.
I'm not sure there is a lot of value in anti-biotics unless there is evidence of infection. Bacterial sinus infections tend to be accompanied by facial pain and/or nasal discharge lasting for several days, with the nasal discharge often being thick, dark and green or yellow in colour. If this isn't the case, then they will do more harm than good.
Sadly doctors seem to have done a complete U-turn on anti-biotics though. I understand why they are cautious, but I think it has gone too far now. 10 years ago, you couldn't stop a doctor giving them out, now, it can be really difficult to be given them even if needed. I had to endure 6 weeks of a chest infection last year before my GP would give me something. By the time he did, I was coughing up dark green mucus many times a day for weeks.
I'm not sure whereabouts you live, but throughout most of Europe, you can obtain steroid nasal sprays OTC. The most common ones are Beclometasone Dipropionate and Fluticasone Propionate. I would say that if you don't feel like you have any nasal blockage though, then again, they may not be for you, but they are generally pretty well tolerated, with typical side effects being drying of the nose lining and nose bleeds and possibly a headache.
Oral steroids are best avoided - generally - but I was desperate and thought it worth a try. I think they did reduce the inflammation a bit, as it was following the course of these that my right ear started to intermittently open. This should only be done under the supervision of a health professional though.
Nasal decongestants should only be taken for 3 days before being stopped as you can suffer a rebound, so I would suggest avoiding them. I found that taking them just once helped a little, but 8 hours later when they wore off, I was totally back to square one and since you can't keep taking them, what good would they be? They can be useful to take before flying though if you have difficulty in equalising the pressure in your ear(s).
Antihistamines might be worth trying, but again, only if you suffer from allergies. If you don't, then they dry out the nasal passages, so they could make things worse. I do occasionally suffer from allergies, so take them as and when needed, but I don't take them all the time.
Anti-inflammatories might be worth trying, but I didn't notice any appreciable benefit over the 2 days I took ibuprofen. Perhaps I should have taken them for longer, but they were giving me indigestion and I wasn't convinced they were doing much good.
Oral decongestants did work quite well for me. I took them twice a day for several days and they really kept things open, but as soon as I stopped, things went back to before. Had I kept going for longer, would they have helped more? I honestly don't know.
What I would say is that time seems to have made the biggest difference. Back in Jan 2015, my right ear was totally blocked. I could barely get air in and out and periodically it would be bad enough to draw fluid from surrounding tissue and fill with liquid. Even then, because it was intermittent, the eNT would do nothing. Over the past year+, this has slowly improved to a level whereby it feels completely open around 20% of the time and the more open it is, the quieter the tinnitus. I have no reliable explanation as to why it opens some times and closes others, although I am aware that the whole nasal lining is a very blood rich area and hormonal changes and allergic reactions can quickly and significantly cause it all to swell significantly.