duckling with injured leg, please help

Please can we have some advice, we live in Suffolk , United Kingdom, We found an injured duckling approx three weeks old that had been attacked by a dog. We took him to the vet and he gave us Baytril antibiotic and iodine for the wound. We have looked after him for two weeks and he has lived in the house with us with permanent care. He has a severe injury to one foot and leg. He struggles to stand, walk, balance. We have taken him back to the vet today for more help. A different vet saw us than the last time we went. He told us he had to be put to sleep because he will never have a normal life. We are devastated, we love him dearly. The vet we saw before said we may end up with a pet duck but this last vet was adamant he had to be put to sleep. Is there another option, can anything else be done? He is holding the foot up in the air when he tries to stand and it is curled over. The vet was unable to determine if he was or was not in pain. He just said there is no point as he will never be like other ducks. I understand he has little movement, will this ever be likely to get better or easier for him. The vet said putting weight on the bad foot when he gets bigger will make it sure and damage further. Otherwise he is in good spirits, we work from home so he has company most of the time, but not other ducks company. Please help. Can he have a life or are we not helping him in the long run?