I liked that Sean talked to the crew before doing the firing, because they are the guys dealing him on the deck and, most important, they are the ones who will have to do more work. It showed respect for his crew and they seemed to appreciate it (and to be supportive of Sean). I think it was a terrible idea, however, for him to tell the guy that everyone wanted him out. Getting the crew's input is good people management; not owning your decision as the boss is not.
For reasons I can't really explain, I think Sig might be more likely to give Mandy the wheel than either Jake or Edgar. Maybe it's that to me, Sig has always seemed to think substance abuse and addiction are a weakness and he struggles to respect someone who's battled those issues? Or maybe he's just a dad who thinks his baby girl can do no wrong!