Thanks rruaco! I ended up changing the itinerary to MKE-ORD-SFO-LAS to make it only United segments, and all these reflect the "A" class apart from the MKE-ORD which doesn't have a first cabin, and is instead in Y fare class. Yes, it is booked as a revenue first class, so even though it reflects a fare basis of HUAUPN, the agent confirmed that it will be credited as an A fare, thereby earning 300% miles with Aegean. She said that there is no separate fare basis that begins with the letter A and that they use one starting with H instead, but it will credit as a first class fare.

Joshua, yes, booking code F on United does earn 300% miles with Aegean, as long as it is on United metal.