Hi, Dennis - and welcome!
I regret that an acoustic neuroma diagnosis brought you here but since it has, I'm glad you found us. - and thanks for the kind words.
As you know, your AN is small so observation ('watch-and-wait') is a practical choice at this time. However, if the next MRI does indicate growth, you will want to seriously consider addressing the tumor sooner rather than later. Radiation will very likely be a viable option for you (your doctor will decide if that is the case) and there are various forms (your doctor may suggest one over another). Radiation treatment does not usually affect hearing so whatever you have now will likely remain, post-radiation. This means that, should your hearing decrease in the next few months, you would want to urgently consider going ahead with radiation treatment to address the AN. This assumes that your doctor agrees that you are a good 'candidate' for irradiation. Although it sounds scary, being SSD (Single Side Deaf) isn't the end of the world, as I and others can attest. However, with 70-80% of your hearing intact, I doubt you have to worry about losing (all) your hearing in one ear and I'm sure other posters will be along soon to elaborate on the radiation procedures available to you.
Jim