What you need to remember is that it isn't a question as to if your dog is a predator or not: he absolutely, definitely, biologically IS. That does not mean that he can't be trained to interact peacefully with chickens under supervision, but it also means you can't be mad at him for acting like a dog. Mad doesn't get you very far in training.
Rather, you need to do two things: you need to make sure your dog realizes that the chickens are YOURS and he may not do what he pleases with them, which can be tricky if your dog does not already respect your authority (so hopefully he does!). And you also need to focus on making being good around the chickens FAR more rewarding to him than being bad around them. That can be tricky: not too many things are better than something as tantalizing as chickens. In my experience, when it comes to something very tempting, you generally need a very good reward AND a very good deterrent used together. And you need gradual introduction, constant reinforcement, and the understanding in the back of your mind that even the best behaved dog is still a dog and can not really be 100% trusted with chickens unattended.
Do you have someone who could help you with introductions? I'm still working on the first steps at the advice of our trainers, but you need to be able to prevent the dog from hurting the birds with his mouth OR paws while still able to see, sniff, etc. and simultaneously offer corrections for bad responses and rewards for good responses. It is generally at least a two person job to do safely.