"There is no post hoc explanation that makes Abraham a good person for almost killing his son by the demand of his powerful benefactor."
I understand this to say there is no explanation that makes a person good for killing another person because someone demanded it. By this reasoning, there is no post hoc explanation that makes God a good person for killing his Son by the demand of Himself. The two stories (Abraham sacrificing Isaac and God sacrificing Christ) are very closely tied together.
If you read the Book of Mormon and Pearl of Great Price, then you should also know there is a Joseph Smith Translation to the Bible. There is one the specifically covers Lot's proposition: http://lds.org/scriptures/jst/jst-gen/19?lang=eng. You are right that no righteous father would ever give his daughters over to a crowd to be raped.