Few questions on call ducks and raising

I have two main questions on call ducks...First how do you treat few day old babies for lice? I have never had any of my babies have lice before, but these 2 call duck babies are being raised by my silkie hen and I am not sure if that is why they have lice or what, none of my other silkies have lice but this mother seems to have a few on her and so does her two babies. I usually treat my chickens with that seven dust....but didn't think I can put that on 2 day old babies. Second question I have 2 call duck hens, a magpie hen, and a pekin hen in my pen together along with my call duck drake and he attacks the babies, and continues to attack (bite and fling around) until the mother hen or myself gets him off. I know have him crated, but is this normal? I have never heard of this and never had problems with my pekins when I raised them. ???Any advise and help would be much appreciated!