Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Size
FORMULAOBJECT_SIZE
Parameter: Effect
FORMULAOBJECT_EFFECT
Parameter: d(u,v,x,y,z,t)
FORMULAOBJECT_DLT
Parameter: X(x,y,z,t)
FORMULAOBJECT_FX
Parameter: Y(x,y,z,t)
FORMULAOBJECT_FY
Parameter: Z(x,y,z,t)
FORMULAOBJECT_FZ
Parameter: Fit to Parent
FORMULAOBJECT_FITTOPARENT