Hi, Boxer ~
Unfortunately, there is no credible method of predicting facial nerve damage due to AN surgery. The small size of your tumor is in your favor but until the surgeons can actually see and address the AN, no serious predictions can be made,although I wish we could.
I think every AN surgical patient has this concern (facial paralysis). I certainly did. My concern was amplified by the fact that I was diagnosed with a 4.5 cm tumor that was pressing on my brain stem. Like you, I had lost all hearing in the affected ear and, as you might expect, I had other symptoms.
In my case, the neurosurgeon had 30+ years of experience with the surgical removal of acoustic neuromas and he promised to do his utmost to help me avoid facial paralysis. He opted to 'de-bulk' my large AN, leaving a little over 2.5 cm (to be radiated, later) but in the process, peeling off layers of the tumor, making it much more vulnerable to the effects of the 26 FSR treatments I underwent three months later. Going in, like you, I was healthy (but 20+ years older).
Long story short; the surgery went fine and I suffered no facial paralysis or even a headache. My symptoms disappeared, immediately. The radiation was uneventful and today, almost eight years later, I'm doing fine, although I remain SSD, as was expected (I cope).
I offer my account of AN surgery on a much larger tumor in a man much older than you to demonstrate that these daunting surgeries can have a good outcome. In my case, I give much credit to, in this order, prayer and a very skilled, experienced neurosurgeon who cared about my quality of life, post-op.
I wish you the same good outcome but should any facial paralysis occur, remember that it is usually temporary and can be alleviated with facial therapy.
Of course, you'll have the support of the folks on this forum so please try to keep us updated, if you can. Thanks.
Jim