Cola, you've already received some excellent advice, so I'll just add a couple things that expound upon and shade what others have said:
1. Meniere's Disease presents, in part, as low-frequency (bass tones) hearing loss. If you're losing hearing in the high frequencies only, you can rule out Meniere's Disease. Definitely have a qualified doctor, or doctors, check for NF2; the symptoms in your left ear are consistent with those for an AN, but idiopathic neuro-sensory hearing loss (without known cause) can also cause these symptoms.
2. While it's true that your tumor is likely to grow over the many years you likely have left (barring a car accident or some other horrible mishap), it is possible it won't grow. The famed Dr. Derald E. Brackmann of House Ear Institute once told me he has seen some ANs that didn't grow for 20 years. I would suggest waiting until either you see an increase in size in followup MRIs or your symptoms get noticeably worse before you seek treatment, as treatment itself can often cause long-lasting side effects. If, for example, your hearing begins to get worse, I would get treated quickly to help prevent any further hearing loss. In the meantime, do exhaustive research on your available options so you are ready to pull the trigger should you need to get treated. This forum is a rich source of information, as well as moral support.
Btw, the "wonkiheadedness" you are describing is known technically as disequilibrium. It may improve (possibly dramatically) over time, but is not likely to go completely away. It is often the worst at the onset of symptoms, and then the brain adapts afterwards. Vertigo is something different and presents a spinning sensation; vertigo sufferers often report seeing the room actually spin. Some AN patients also report having oscillopsia, which makes your vision bounce up and down as you walk. I had all three symptoms: vertigo, oscillopsia and disequilibrium. But now I just have disequilibrium as you are describing, and it's very mild -- sometimes all but unnoticeable -- on most days.
Best wishes,
TW