Good morning i just wanted to update he is so much better doesn’t eat that much but he is walking thank very much for all your helpHow does his wound look? can you get a picture of it or them and is there any smell or oozing he may have infection. Of course if the dog grabbed him his body is most likely very sore but the only thing I can think of to get him to eat is tube feeding we have info if you want to try but you'll have to get the things together before you start.
https://www.backyardchickens.com/threads/tube-feeding-ducks-updated-5-7-2020.1211994/