Sorry can't help with the DFFWSC vs CFFWSC booking question. But I did notice a RT fare ZSFSC (similar fare rules) that is priced below the C OW fare. With a 360 return, that could be interesting.
This is the fare I see filed:
V FARE BASIS BK FARE TRAVEL-TICKET AP MINMAX RTG
1 DFFWSC D‡O 2287.00 ---- -/‡ -/ - AT01
PASSENGER TYPE-ADT AUTO PRICE-YES
FROM-SEZ TO-HNL CXR-DL TVL-01JAN14 RULE-WBFF IPRA/1
FARE BASIS-DFFWSC NORMAL FARE DIS-N VENDOR-ATP
FARE TYPE-BU OW-BUSINESS CLASS UNRESTRICTED
SCR 27028 MPM E07JAN12 D-INFINITY FC-DFFWSC FN-
SYSTEM DATES - CREATED 06JAN12/1637 EXPIRES INFINITY
PUBLISHED RTG SEZ-HNL/DL EF-07JAN12 DIS-INDEF
/VIA THE ATLANTIC/ MPM 15027
MILEAGE SYSTEM APPLIES BETWEEN ORIGIN AND DESTINATION
MILEAGE SYSTEM APPLIES ORIGIN TO DESTINATION