Is it lust or aggression from my drake?

I have had my muscovy Ivan (was told he was a mule but I can't tell) since he was a few days old and he is now about 6 months old. I have handled him every day, though not excessively. He was raised with chicken peeps his same age, paying no mind to my 3 slightly older Pekins. When he was about 4 months old, he was trying to mate the big older chickens, rather brutally- much rougher looking than my Pekins behavior to each other. I put him in a separate pen and got him his own beautiful muscovy hen, to whom he pays little mind. I don't let him out of his pen much anymore as he had a tendency to stand in the road.

For the past month or so, he's been nipping at me progressively harder. It started with him tasting my shoes, then light tugs at the bottom of my pants. It generally didn't bother me and I didn't perceive it as aggression. Sometimes I would pick him up, sometimes I would hold his bill. He's my only duck out of 5 that I can walk up to and just pick up and pet. Lately, he's been biting the tops of my rubber boots and grabbing my pants and yanking really hard, sometimes holding on for a while. He quacks non-stop when I'm around and follows me around the pen trying to nip around my knees (good thing it's been cold and I've been wearing padded overalls and tall boots). Sometimes I pick him up and hold his bill closed for a few seconds, or else I nduge him away with my foot.

I plan on getting one more muscovy hen for him (as well as more company for the sweet shy hen Clarabel)-the muscovy pen is only 10 x 16- and am thinking of merging the pen with the adjacent pekin area if they get along. (I'm a little reluctant to do that as I have 2 pekin drakes/one hen and the trio gets along so perfectly-but they do stare at each other through the wire partition now).

So is Ivan going through a nasty teenage boy phase that he'll grow out of? Is it a dominance thing? He doesn't have much contact with other people although this behavior started with my fiance, who I keep away from Ivan now or Ivan will get kicked hard. Is Ivan in lust with me or mad at me from separating him from his true loves, the chickens, who occasionally wander by his pen? Is he mad about being penned up all the time (it's been almost 2 months now), whereas I used to let him free range during the day? One muscovy hen hasn't distracted him-will getting more help?

I'm not an aggressive person so it's not in my nature to just kick him away all the time or to do something really hard "so he doesn't forget". But I'm open to non-violent suggestions if I need to show him who's boss: duck psychology, behavior modification. Freezer camp is definitely not an option- I haven't eaten any birds at all, of anyone's, in ten years, and I've only raised chickens and ducks since this April. I'd prefer not to re-home him as I get all misty eyed when I look at his baby pictures, sleeping on my lap.

This forum has been really helpful to me as a newbie; I read it all the time although I've seldom posted. Thanks so much for any input.