I find your case a little puzzing.
Did Post say he thinks he can or cannot get to it via Retro?
I think Mid Fossa almost always give you the best chance of hearing preservation, but perhaps because of location it might be better for you either way. Dr. Galfinos offered me that option also. However, for the slightly higher probability of hearing retention, he said there was a tradeoff of slightly higher probability of facial problems (at least in my case). That's why I chose Retro.
Galfinos gave me exactly 50% using Retro.
Post initially gave me 50%, but then upped it to 70% after seeing the results of additional tests.
Smouha, after consulting with Dr Post, reviewing my MRI, and seeing the results of the tests said (paraphrase). "Dr. Post is a little more optimistic than I am".
I came out with very good hearing.
So 50% is 50%!!!
IMHO, 50% is actually more than 50% because they don't want to raise your expectations too high and then disappoint you. It's obviously no guarantee, but it's not like you are definitely SSD. Plus, from what I gather and from my limited experience right after surgery, SSD is not quite as bad as the initial shock of thinking about it.
I recommend you get some more feedback from those here that know before making a decision (including the Baha option that would help for your work)!
Finally, I don't understand the radiation recommendation from Galfinos unless he gave you a specific reason. You are younger than me (I'm 50) and that was a primary consideration. I specifically went to see Galfinos because he does both and I wanted a neutral opinion. Dr Post admits he is biased towards surgery (as is Smouha). Galfinos gave me the pluses and minuses of both and said I could do either but was hinting strongly he thought surgery was best for me. So I don't understand the thinking or specifics in your case that would make it different. hmmmmn
By the way, I considered talking to Sisti, but i seem to recall that someone suggested to me that he's more of a cancerous tumor specialist than an AN specialst. Perhaps he's both.