I just noticed in your pictures you are measuring the outside tire of the turn.
The Steering angle that seems to work the best is the inside turn angle, the outside wheel travels a bigger circle so it does not turn in as far. Guessing this will add another 10 degrees to the 30. I call the angle magic because this was my last big fix before U turn worked properly.
I know all the letters are flipped, but the picture is top down, not quite as good a draftsman as you awesome linkage drawings!