Just as a very quick answer to the last part of that, there should be a liberal smattering of Flakvierlings around the current version of the airfield... Are they not appearing?
I am aware that the whole island was turned into a fortress (torpedo launchers on land? Okayyy...!) but haven't even looked into that yet, because it would require modelling. I'll come back to it when I can.
Cheers,
ian P.