Your assumption that a fertilized egg is a human being is ridiculous. Who told you that a fertilized egg is a human being? Whoever did that, knew squat about human biology. And you think you are a medical doctor?
As for your poetic reference to the Faustian bargain, well, I don't know what soul is, so I don't know what mythological mumbo-jumbo you are talking about. As for morals, my morals are superior to most of the Bible book club members.
There is no assumption just fact. Human life begins at sperm-egg fusion this is an uncontested scientific and objective conclusion. Furthermore it its a conclusion reached independently of any ethical or religious view of human life.
Development and growth is a continuous process but your attempt to argue that early human life has no value is logically flawed. Your personhood criteria a stage where you feel young human beings are suddenly deserving of being extended basic human rights is utterly arbitrary. You have deliberately avoided defining it because you know its arbitrary and that there is no solid scientific grounds for making such a distinction. Life begins at conception.
In regards to your claim of moral superiority... Well lets just say we I think you are doing a good job showing us all what your morals really are.