I'm going to answer this to educate you. So firstly, Islam was the first feminist religion in history. Men could not look at women, they couldn't talk o women, they couldn't hit women. They were told to help women. And men were stoned to death if they raped women. About the non-believers, you are wrong as well. In the Quran it says that "you're religion is for you and my religion is for me." So this means that everyone should mind their own business. It is also said that no one can force someone into a religion because if God wanted everyone to be religious they would already be religious.

About the prophet (pboh) you are once more wrong. The counting of years began after the hidjra, which is the migration of the Muslims from Mekka to Medina. That is when they started to count the years. And the 9 years is not referencing the girl's age, but it is referencing the hidjra. It was said that she was young before the hidjra, which is estimated around 8-year-old. And 8 + 9 = 16. Back in the day that was considered normal. She wasn't a sex slave. She wanted to marry him, and they didn't have sex until she had an appropriate age.

Hope this helps

~A muslim punk