What role did things like religion, folklore, and family life play in the lives of slaves?
Historians say that things like these were important things that the slaves did to make their lives less oppressive and to help themselves cope with their enslavement.
Historians today like to emphasize that slaves did not simply take their enslavement passively. Instead, they resisted in various ways. One way was by making as much as they could in the way of a community for themselves. All of the things you mention helped with this. All of these were ways of making connections with other slaves and of giving the slaves a way of making the best possible life for themselves in a horrible situation.
Religion gave the slaves something to look forward to after their hard life. That someone still cared about them even though it seemed as if no one els did. Family also gave them something to be happy about but of course the families could not get to atached on the account of when slaves where sold their families were split up, mostly never to see one another again.