Nice looking product. When I make this type of sausage I take the meat out of the smoker when the temperature of the meat is 130f
After removing the meat I put it in a water bath that is 180f. until the internal temperature of the meat reaches 160f. then cool in ice water.
I think that when you leave the meat in the smoker until it reaches the final temperature it dries the outer layer of meat and makes it hard. I would not leave out the binder when you make your next batch.