Yeah you have a point with how the refusal seemed ambiguous, I remember at first where I thought The Count did sacrifice his daughter due to him saying "No.. I don't want to die" but when she was spared I was quite surprised.Walter said:The Count didn't "refuse" so much as "hesitate" to sacrifice Theresia, until he bled out and died. Miura chose to make it more ambiguous than an outright refusal to sacrifice his own daughter, which I think is pretty important given the kind of monster the Count had become.
And Femto didn't try and threaten him, he was telling him exactly what would (and did) happen to him if he died there.
Threaten was not the best choice of words then in that case, my mistake.