Making independent decisions is far from unique to molossers. The emphasis with poultry and any tightly confined stock needs to be on defending the location. Defending herd which molossers were developed for provides no advantages in a backyard setting. OP decidedly backyard with a tractor...
The dog need not bond to chickens, rather is must not cause them harm which should be trainable especially once the dog is pushing two years of age. The OP may not be well suited for that.
The dog is suffering boredom to an extreme and is in the terrible two's that applies dogs like you are seeing. You are not setup to use a standard sized LGD. Dog quite salvageable but another party may be needed to do it.