A non-polar solvent means just that - no 'charge' at all on the molecule. Naphtha is a nonpolar solvent, like toluene and DCM.    Most alcohols are polar and will mix with water. IPA will not be good to extract dmt-freebase.     Water at pH 2- 4 is used as a polar solvent to dissolve dmt-salt - I can't see any use for IPA in an extraction.    Acetone is less polar but I don't believe it's considered a real "non Polar" solvent either.