You are really something
One of the first people to accept Islam was Hadhrat Bilal, a slave. Why would he accept a religion if the very thing he ran away from was also practiced by Muslims? Jesus Christ, where do you get all this from?
Stoning is not allowed by Islam, it was only practiced, in accordance to Jewish law, until relevant instructions were revealed from the Qur'an.
The women you're referring to as "slaves" were women who were prisoners of war. Rather than imprisoning them and treating them like shit (which they would have had it not been for this) people were given the permission to marry them and have them as wives. With this they were allowed to carry on a decent and normal life (as normal as you can have as a prisoner of war).
The entire concept of having four wives is not so that you can sleep around. There are different circumstances under which you are allowed to marry more than one wife. None of which include to fulfill your perverted sexual fantasies. The reason why women can't marry more than one man is because most cultures follow paternal lineage.