Oh my, your encounter with the weasel attacking your birds is very, very close to my own, but with a mink, from just last month!
I have a mixed flock that all bed down in the coop at night as well—chickens, ducks, and a guinea. My husband heard the guinea squawking around 3AM or so, and went outside to investigate (once he left the house and was heading to the coop he could also hear one of my ducks screaming in pain

) He opened the door and when he did, my Pekin literally rolled out the door and onto the ramp, with the mink still attached to his neck!
My husband had nothing in his hands but his Maglite, so he beat the crap out of that mink with his light until the mink released Mr. Quackers. The mink ran back into the coop....much to his own detriment. Wherever the mink had come in from, he could not find his way back out, and by then my husband had ran back to the house for his .22. He was able to dispatch of the mink while he was trapped in the coop, meanwhile I had herded all the birds out of it.
I lost one of my ducks too, a male Rouen named Dewie (I have 3 Rouen, Huey, Dewie and Louie...), but thankfully Mr. Quackers survived. The wounds to his neck were pretty deep and serious, but we worked with each other to nurse him back to health while he lived on my kitchen floor for a while. A month later and he’s back to his old self
I would definitely find out anything you can about capturing and dispatching that weasel before it goes for another round. Weasels are very active during the winter, and since they don’t store body fat like other animals that are active during winter do, they need a constant food source for energy. It now knows there is food to be had in your coop, so it will want to hit again. And given your wooded surroundings...there’s going to be more than just the one.
Good luck in stopping this weasel and protecting your birds. I’m sorry about the loss of your duck