First of all, reduce AI traffic (I recommend max 50-60, parked cars - 25%) and Sheduled AI buses (half of them).
And, of course, do not reduce The Max FPS Count to 55, just up to 25.
(I hell ain't know how you can get more than 30 fps in such big maps, and how about 55
- Max Tiles Count to 2 (or even 1)
- Max Object Visibility to at least 250-300 if you still want this map to look 'somehow'.
If you give us your hardware specification, that would be easier to help you.
You can always try to load already prepared setting presets (I mean, For 2006 PC, 2007 PC and so on).