You could try lowering the FPS. For your field of view, 10 FPS is probably sufficient.
Unfortunately, bitrate probably cannot be lowered any as it is and this is one area where you can tell the CPU is underpowered - most of the 4MP need 8192 bitrate, and this 8MP caps at 8192, which can degrade the image in certain fields of view.
Unfortunately, bitrate probably cannot be lowered any as it is and this is one area where you can tell the CPU is underpowered - most of the 4MP need 8192 bitrate, and this 8MP caps at 8192, which can degrade the image in certain fields of view.