Hi, I'm from gemini server and my team sells DS & JS (250k + rep pot) for FB I have'nt actually thought about selling it but for me the best way to sell it is by per stage, like 1.5m per stage its a hard quest and chances are you are not going to be able to finish it in just one sitting.
As for 92 fire wit, yup I have to agree, its not really that useful when doing FB quest. Our team compose of 4 - 130rb++ and 6 - 100++rbs and sometimes we were having a hard time doing it. As of now we have only finished the quest on 3 of my alts.
Thanks have a nice day.