There is no way to avoid the various nerves using SRS. Since they are essentially in the way, they do receive a dose of radiation unavoidably, and this is why radiation may result in hearing loss and (more rarely) in some facial nerve problems. This is why fractionation is considered by many more beneficial, since it allows the healty cells to heal, before receiving the next dose.
Simplistically speaking, depending on the SRS method the maximum dose is delivered at the centre (for example in GK), but the amount declines sharply at the edges of the tumor, so that the surrounding structures are not affected. CK is considered to deliver a more uniform dose.
I am a bit surprised by the statement that your AN is only 2 mm from the brainstem, this seems too close for a tumor of your size. Perhaps the doctor meant the cerebellum? Some doctors are very vague and not forthcoming, and this is frustrating, but this is their style.
Regarding the symptoms, what you describe is not unheard, especially so early after radiation. Typically symptoms tend to crop up within the first 6-12 months. I am a bit surprised by the fact that your next MRI would be in one year, I think that standard here in N. America is 6 months after radiation treatment, depending of course on the doctor's judgement.