Mapping Center Answer:

Okay--first I think there's a bug here because what you had, with one change should have worked.  That change was to turn off the Never Remove Labels setting. 

I made five other changes that produced a better result (the first 3 had little consequence):

1. Reduced the feature weights from 1000 to 800 (this helped with labeling the linear features).

2. Changed the maximum offset to 500% (no point in doing 3500% -- you could get a really ugly label).

3. Optimized your label expression to have two fewer lines:

Function FindLabel ([STANUM])
FindLabel = [STANUM]
IF InStr([STANUM], "-") <> 0 THEN
 FindLabel = INT(Right([STANUM],4))
End If
End Function

4. The big one was to adjust how you were using user defined zones.  I just used the 3:00 and 9:00 positions--giving them a rank of 1 and 2 respectively.  This forced many of the less good looking labels off the map (I noted that most of the collisions occurred in close to vertical orientations). 

5. I changed your point symbol to be a 25pt circle (using the circle symbol from the default style).  Then I gave that a label weight of 800 as well.

I'm not totally happy with the result, but it's much better than before.  The only issue is that Maplex often insisted on crossing a road with a leader--doing #5 alleviated some of that.

I gave this case to the development team to have a look at.

Thanks.