Someone explain Rhysand’s behaviour…

In book 1 when he went to spring court and made Tamlin and Lucien grovel. I didn’t get it. Was it explained in later books? Why did he do it? How was he allowed such free rein under Amarantha’s control/torture as to go wandering and also to dress Feyre up and use her as his plaything UTC?

Also, we were lead to believe that Tamlin was the strongest of the high lords (he killed Amarantha after all) - but I thought this was Rhys? Also, was Amarantha in love with Tamlin? If so, why did she abuse Rhys and not Tamlin? (Not that she should abuse anyone at all….)