Apply for med school and see what happens. I would not lie during the interviews - if your interested in OTO, tell them. After all, you would have much more insight than your typical 21 year old biology major applying who has spent a couple of afternoons "shadowing" some private practive physician. You can relate to enjoying the diagnostic aspects of Otology and that you're keen on providing both medical and surgical management.
One caveat, however, is that it is extremely difficult to get a Neurotology fellowship. And while having an AuD is great, I don't know if it would help in the fellowship match. You'd have to ask your faculty. A majority of applicants these days have significant research (bench) and ~1/2 have a PhD, too. My understanding is that the AuD is more class-room/hands on experience and is now the entry level requirement for new audiologists (as opposed to a masters in the past). As far as audiology training - you'll learn what you need to know in residency (often with a little bit of self-directed learning) and if one ends up in a Neurotology fellowship, then clearly the audiology/vestibular training is much more in depth.
As a side note there are only somewhere around 15-18 neurotology fellowships per year, and all are now 2 years so you'd be looking at a minimum of 4 + 5 + 2 = 11 years once you start medical school, if you don't take time out to do the research required of a neurotology fellowship. A very long road ahead.
That being said, if you like otology, you can do a significan portion of your ENT practice in ears if you go to a residency program that is strong in that area - obviously this would proclude CPA tumors and advanced otology - but you'd be fine with tympanoplasty/mastoidectomy/MEE/possible OCR/possible stapes/etc....
My advice, take the initial steps (MCAT/prereqs/etc) and see what happens.
Leforte