I think that bit in the manual about the vacuum line is a holdover from the older V6 cars that had the vacuum hose connected to manifold vacuum. On the Milano they switched to port vacuum, so there is no vacuum on that line with the throttle at idle (you should see vacuum on the line as soon as you open the throttle plate.)
That shows how long I have been in Megasquirt mode
The advance curve is not controlled by the distributor but by the advance computer so you cannot change it. You can shift the whole curve by rotating the distributor. I don't remember what the max advance is but I can tell you that on a dyno my 3L motor with "S" pistons made max power at 34 degrees. A lower compression motor might need a shade more. You should not run into starting problems if you keep the static below about 12 degrees.
76 Suzuki GT500
2011 Jaguar XKR
A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke