[Juha]

Hello Jon
2)Germans used 7,9mm mgs to the end, even He 177s had them, in A1 Stand (MG 81) and often in C-Stand (MG 81Z), He 111s had them to the end as beam weapons and usually also in C-Stand (MG 81Z) even if the late versions had heavier weapons in A- and B-Stands. Also Ju 188s had usually MG 81Z in C-Stand.

1)to my understanding there were no or only a few A-4s flying in 1940, most were A-1s and A-5s.
Ju 88 A-5 had A-Stand (forward firing) MG 15 with 450 rounds (means 6 saddle-drums)
B-Stand (upper backwards) 2 MG 15 with 1125 rounds (means 15 saddle-drums)
C-Stand (under backwards) MG 15 with 600 rounds (means 8 saddle-drums).
A-4 (early) probably had the same armament than A-5, but at least later A-4s had MG 81s, which were belt-fed.

I have not time to look at He-111H, and I think that I don't even have that info anywhere.

HTH
Juha