Hi Chrisaliz, and welcome to the Forum.
Only two girls is rather a small number for an active cockerel, especially as he favours one of them. He really needs about four-five to help spread the load, but I realise this may not be possible for you. It does sound as if he's rather too hard on her. Once he started to draw blood, she will be in trouble, and anyway it's not good for her to be so much bullied. You will need either to separate him, or separate her, perhaps by making a mesh barrier across the run so they can see each other but not get in touch. If you do this it would be best to keep the two girls together and the cockerel on his own, so he doesn't start on the other hen. Then you will have to decide what to do about the cockerel. Is there a particular reason for keeping him? The hens will be happier and more peaceful in their own and will lay better without the stress. What sort of birds are they, and how much space do they have in their run, in square metres?