My Muscovy drake Ivan (aka Ivan the Rapist, Psycho Duck but usually just Good Duck) has some of the same behaviors, but not as aggressive. He was raised with silkie chicks and last year tried to mate some of the huge Cornish X hens, so I think he definitely has identity issues. I got through to him that that wasn't allowed (picked him up and took him to time-out alone in his pen) and got him his own Muscovy hen. He doesn't pay her much mind. When everyone is out free ranging, Ivan will hang with the chickens and attack one of the top roosters. My Pekin drakes try to attack Ivan-they are enamored with the Muscovy hen and must assume she's Ivan's woman they must take by force (but they are thoroughly respectful of the Pekin hen). Ivan looks kind of dopey then as if he should defend her but is too wimpy to do so, even though I'm sure he could kick the Pekins' butts if he were so inclined.
But I am his main love interest and he'll follow me all over if I'm in sight. The foot and leg biting comes in fits and starts, 95% of the time it's not too hard. I pick him up and carry him around a bit. When I have time I'll sit in a chair with him standing in my lap for maybe 10 or 15 minutes. He NEVER tries to bite me then. He completely relaxes and will eventually jump down or fly off. I haven't been able to eliminate the nipping issue but he just hasn't been annoying enough to me to pursue it further. My fiance gets thorougly ticked off when it happens to him, but getting in a power struggle with Ivan seems to make his aggression far worse, with giant wings flapping at you and sharp Muscovy claws getting snagged on you.