So did you come up with any alternate solutions?
I ordered a different DC to PWM circuit board that I am going to try out. I was even thinking of buying this thing labeled as LED dimming controller, but that's $30, and I fear the same results as last time. I'm not really sure what's going on with the module I tried. Like I said it works in the opposite manner, but it actually works better than the factory radio. The range of brightness was much greater.