From the A/C point of view, the difference between low and high speed is the engine RPM. This makes the A/C compressor run at higher RPM too and higher pressure in line. In your case, it is VERY likely your problem is the expansion valve in the front evaporator. It needs to be replaced.
The cabin filter has nothing to do with your issue. Just think about this, when you want MAX A/C COOLING you put the A/C air in recirculation. Recirculation stops all external air to the cabin by closing a flaper. Therefore, the cabin filter is removed from the picture.