PWM is based on zero to 100%... you're aware that you're not going to get too many tenths if you're using 256 bit resolution?

The best is 100/256 or steps of around 0.39%... falls well short of tenths.

I would suggest using a PIC with hardware PWM as it's 10-bit and you'll get tenths of a percent there (100/1024=0.0976% steps).

Melanie