Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Strength
EXPLOSIONOBJECT_STRENGTH
Parameter: Speed
EXPLOSIONOBJECT_PSPEED
Parameter: Angle Speed
EXPLOSIONOBJECT_ASPEED
Parameter: End Size
EXPLOSIONOBJECT_ENDSIZE
Parameter: Randomness
EXPLOSIONOBJECT_RANDOM