Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Daylight System / Physical Sky
SKPIMPORT_DAYLIGHT_SYSTEM_PHYSICAL_SKYParameter: Camera
SKPIMPORT_CAMERAParameter: Skip Hidden Objects
SKPIMPORT_SKIP_HIDDEN_OBJECTSParameter: Split Objects by Layer
SKPIMPORT_SPLIT_OBJECTS_BY_LAYERParameter: Show Statistics in Console
SKPIMPORT_SHOW_STATISTICS_IN_CONSOLE