Hi Owain,
I take your point about the deck angle. +3.5 degrees is a much higher "rigger's angle of incidence" on the A320 than I realised.
On the apparent, katabatic-like performance of the incident flow in the OP's example: if 1.9 degrees seems reasonable, what about 3.5 degrees? Combining the pitch of +2.7 and the AoA of -0.8, I make it the latter.