How do I gain independent controls about manipulating the values of the 3 bands (high, mid & low) of this API (Superpowered3BandEQ)?

Change the values of the bands public attribute. Bands[0] is low, bands[1] is mid, bands[2] is high. Documentation: http://superpowered.com/docs/class_superpowered3_band_e_q.html