I agree the provenance story seems compelling, and I'm pretty sure the gunners and lower portion are real. The Stuka and in particular the smoke just don't look like they are the same picture. I tried to find other pictures of smoking Stukas and none of the pictures of crashing machines seem to have any, or there is a massive amount of flame accompanying it. Not saying that is proof in itself, but the Stuka and the smoke is really bugging me. The smoke looks cartoonish in the colorisation and not enough visible in the B&W to compare it.
The blur on the Stuka does look like pictures associated with gun cameras, in those the whole picture is slightly blurred not just the target.