I had the same problem with my runner drake...but I just put up a short fenc (1') since he can't fly...it worked to have him in his own yard. Then I got him another female too.
I've since let down the fence, and he chased off the chickens when they got close to the female ducks...so he kind of learned to be a duck (sort of). It's like he didn't know the difference until it was forced on him for a while. I did notice that when he chased the chickens, they quickly figured out if they got up onto something he coudn't do anything-- so depending on how high frodo can jump/fly, you may be able to give the chickens safe havens by having a couple of saw horses out there or a leaning ladder or something else.
Coons took both the females recently...and my drake now trying to be a chicken, but hasn't tried to mount any of them. I figure it's a matter of time....I"m looking for grown females as I type!
ALSO- have you thought about asking the zoo if they have a few extra females? Tell them the situation and they may be willing to trade....
Sandra