Seems like you have found everything ok, and in my opinion at least everything you say seems about right.
The bentley E34 5 series manual contains all this info, and much more, but as its american doesnt contain data on the 2.0 engine, or the 1.8 for that matter, as the yanks seem to have classed the 2.5 as the base level engine.
I'd contact the club to see if they can help you obtain a good manual for the 520, dont bother with the haynes, its about as much use as a roll of andrex on our cars.
The chap who does books etc from the club is called david, but they will give you all the details, even if you arent a member, although you get a discount if you are.
The parts chap for the club works for a dealer, he may also be able to help, also I have seen cd's advertised on e-bay, but I'm not sure how good they are.