[ChrisMAg2]

As for second:
The MK 108 had rather low rate of fire (therefor it was nicknamed "pavementbuster" by US-pilots). And usually you would only carry arround 90 rounds per gun. The max range was IIRC arnd 2000m, but it was practically used within 300 - 400m. Not much nearer because of debris, not very much further away because of the ballistik curve and deviation.
AFAIK the couped aiming devices for this guns were set at around 300 - 400m in avarage.