The reasoning is thus: Angelo asks, whether there might not be a charity in sin to save this brother. Isabella answers, that if Angelo will save him, she will stake her soul that it were charity, not sin. Angelo replies, that if Isabella would save him at the hazard of her soul, it would be not indeed no sin, but a sin to which the charity would be equivalent.
II.iv.73 (56,7) [And nothing of your answer] I think it should be read,
And nothing of yours answer.
You, and whatever is yours, be exempt from penalty.
II.iv.86 (56,9) [Accountant to the law upon that pain] Pain is here for penalty, punishment.
II.iv.90 (57,2) [But in the loss of question,] The loss of question I do not well understand, and should rather read,
But in the toss of question.
In the agitation, in the discussion of the question. To toss an argument is a common phrase.
II.iv.106 (57,4) Better it were, a brother died for once, Than that a sister, by redeeming him. Should die for ever.