Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Strength
EXPLOSIONOBJECT_STRENGTHParameter: Speed
EXPLOSIONOBJECT_PSPEEDParameter: Angle Speed
EXPLOSIONOBJECT_ASPEEDParameter: End Size
EXPLOSIONOBJECT_ENDSIZEParameter: Randomness
EXPLOSIONOBJECT_RANDOM