LPF should be set between 80-100.
As for your gain being under half that doesn't mean much. It could still be clipping, your head unit could be clipping, the song your listening to could be clipped, etc. Buy a DD-1 or a scope and find out when your HU starts to clip, then tune your amp to clip at the same time as the HU, and play only music you know isn't clipped like Decaf or BigPimpins stuff.