If you go back to the basics with this dog you may be able to get him to bring his reward to hand.He needs to reprogram himself thatyou are the man not him . The real reward for him needs to be when he brings the rabbit to you he will be rewarded with the positive stroking he lives for . I would put him on a 30' lead in the yard. The lead will give you control and give you that long arm to help him understand what you want and make the dog come to you. Placea freshkill rabbit in the yard ordo things the same as you would do in the field ( set up your own little hunt as you will ) .His problem is not the rabbit, it is the retrieveor the programing that he needs to learn to bring everything to you .Work him twice a day on this for a week with rabbits or any thing he has come close to eating .
Just my opinion . I have a golden that did the same thing with doves ,
so I started over with him and we have'nt had a problem since , when I see him start to go back to his old way , we start right over with repetitive training of retrieving and returning to hand. LG