You're right for the most part it is incredibly accurate especially roofline, windows, sidewalls, wheel wells really very nicely done! Proportions are spot on!
Some other things I noticed (I'm on my 4th or 5th E30 now so can't help it when I see one in 3D):
1) Mirror is actually square so bottom line is correct only there's a second one sloping from mirror casing down to the 'triangle'.
2) As charging car mentioned the line flow is perfect only the indent is a bit thick. Crease on a articsilver touring:
3) The standard E30 tourings don't have a crease there, only last edition tourings had a plastic strip above the sill
4) The width of the bumper and the rear apron at that point is actually equal so it should be more or less gapless. Check here with bumper not installed:
5) The rear apron has only minimal angle inward on the sidewalls, again see above picture.
Yeah E30 drivers are crazy me included. Thanks for your work and I can't even imagine what 1.0 will be like
. You really nailed the shape and proportion - hat's off!