"My entire family (except for Amanda) is staunchly pro-life. Her mother is beside herself."
Sad to say but they can stop this abortion today. Even though Amanda is 18 and legally an adult, she lives with your parents. They can answer the boy's parents threat with one of their own - Have the abortion - find another place to live - we will not support you anymore.
You can bet if his parents have this kind of power over the situation, as soon as she has the abortion he will dump her at his parents urging. Then she will have killed her baby for nothing. God help you all through this.
But, she's so crazy about this boy, I don't know if any of that will make a difference. His parents are loaded and they recently bought him a new Camero and have his college plans ready. They told him that they will take his car and will not pay for his college if she keeps the baby, along with disallowing him to see her again.
A real class act, that family.