I find your interpretation of the story to be horrifying.
There is very little detail provided in the Bible for this story. This leaves much of the story left open to one’s own interpretation and understanding. One can fill in the blanks with all things horrible, evil, and immoral; or, one may put their faith in God, believing the Bible to be the word of God, and attempt to understand the story from a higher, spiritual, and moral point of view.
I believe Abraham to be an obedient faithful prophet of God. I believe Sarah to be obedient and faithful to God. Hagar may have been Sarah’s maid, which may mean a servant or a slave, but that does not mean she was automatically treated horribly by Sarah or Abraham. Since the two were faithful, moral, and God-fearing, I believe they would’ve treated Hagar with a great amount of respect and valued her as a person, and not as an animal. I don’t believe Hagar was given to Abraham to wife, against Hagar’s will. I don’t believe Abraham would rape her, either. It’s quite an insult for you to say such a thing about him.