Charles just can't say no to handsome men, god damn it xD I do believe Damiens though, he feels honorable.
And granny is vicious - she accepted Charles-Henri as the head, so the whole fam has to do as she tells them to, or else.
Somehow though, I don't think Jean-Baptiste wants to kill Jack. Why woould he need a bonesaw for it? Maybe he actually wants to use his medical knowledge and amputate a leg (or both, probably) to save the patient's life. Ooooh, maybe that's what he meant, when he said that Jack should've stayed in the medical area -that the treatment wasn't finished.
He had a stroke, probably multiple ones, so voicing his thoughts might be too difficult for him. I might give him too much credit, but he WAS a pro, before falling ill.