About him taking some time to do things. He is planning and preparing. Remember that now that you know what he is, his perception of time differs from a human's. A decade is not a long time for him, so waiting a few days is nothing. Also, yeah, he has a high libido. About Dian, there is a payback, so don't worry. He even says that in the scene. You don't have to choose between Dian and the others.