What a mess Edmund is in. I know that engagements in this era were more binding, and he feels that as a man of honor, he can't break things off with Mary. I do find it curious that as a man of the cloth, he seemingly sees no problem with foisting on his congregation a minister's wife who thinks adultery is a-ok as long as the woman is beautiful. (It also doesn't occur to Edmund that Mary herself is beautiful and would presumably see nothing wrong with committing adultery herself, should she be so inclined.) But it is encouraging at least to see signs of enlightenment from him. He knows he has made a mistake, knows her morals are incompatible with his, but can't stop himself from daydreaming that things might be salvageable after all.
It seems the decision to break things off, if it is to be made, must rest with Mary. Edmund thinks her decision is clear--him or Henry--but will Mary see it that way? Will he have enough spine to convince her he is serious about this? She has a great capacity for setting aside their incompatibilities on the assumption that he will come around to her point of view (and Edmund hasn't been innocent of this either). Would Edmund break off their engagement if he learned of her heartless, selfish views about Tom's demise?