Welcome to BYC. Glad you decided to join our flock. Your rooster should mix okay with the hens, but I would suggest getting some more hens as the recommended ratio of roosters to hens is 1 rooster for every 10 hens. Too many roosters can be physically very rough on your hens; over-breeding them, biting and plucking the feathers from their necks and backs, battering them, and potentially seriously injuring them. I currently have 25 hens and 1 rooster (a White Silkie that someone dumped on our property, and who I intend to re-home soon), and I get lots of eggs without all the aggression, fights, feeding of non-productive mouths, crowing in the middle of the night, and over-breeding and battering of the hens that goes along with having roosters (especially too many). My hens are stress free and seem to be enjoying life without any roosters around. As far as your rooster attacking your Muscovy goes, if it's a drake, it will likely be the other way around. A friend of mine has some Muscovy ducks and the drakes rule the roost, even running larger birds like geese and turkeys. Muscovy drakes are tough hombres. Please feel free to ask any other questions you may have. We are here to help in any way we can. Good luck with our flock.