I always thought that slavery was acknowledged by Christ but not condoned, necessarily. All of the evils of human society were acknowledged, but could be put to good use by God, as it were. If you were a slave, enduring your lot until the end could be a sacrifice to God. I don't know what we should think as far as Church Fathers and monasteries owning slaves or supporting slavery, but C.S. Lewis talks about this briefly in Mere Christianity (I don't have a quote); I think to say that God allows certain evils among men as they grow into righteousness (like the killing of entire races by the Israelites, concubinage among kings and other OT figures, etc.). Gradually it becomes apparent that certain things aren't right, and men move away from them.
As far as how this relates to marriage...I would like to ask if you think love has anything to do with human relationships, or whether you think they all come down to conquest and ownership? Your posts are relentless in a way. Do you think God intended a joyless, loveless existence of servitude for all of us, or what? I don't get what you're driving at with your line of questioning.