I think the answers to your questions are pretty obvious... 8k of bombs would mean that its a med/heavy bomber... the prefix 'Do' is for 'Dornier', a German aircraft company, and history is probably rather short, considering unless it was around before 1940, (which it doesnt look like, based on performance), it would not have seen action in the BoB and probably was not used all that much. It think the answer to the last question is pretty obvious, being that the German bomber fleet is extremely anorexic.