Need help with FPS!

[Dova]

Hello. Can somebody help me and say what options are influencing the FPS in settings? I don't have good PC but it is somewhat enough to play B&S. I have Combat Mode turned ON in options, 1440x900 resoluton (my monitor resoluton is 1920x1080), everything else on on 3 on slidebars (had on 2 but could stand the PS1 graphics), and everything else is unchecked. I get from 25-40 FPS(Rarely above 40, mainly around 30-33) depending on the part of map.
These are my PC specs

Processor: AMD Athlon(tm) X3 455 Processor, 3300 Mhz, 3 Core(s), 3 Logical Processor(s) (overclocked i think)

GPU: AMD Radeon HD 6670

RAM: 4GB

Motherboard: M61PME-S2P
And WIN 7
Screenshots of settings : http://imgur.com/a/M7E35
Can somebody tell me what are the best options to get the most FPS?