Update: Everyone is doing great! I love my chickens!
I decided to start letting the chickens out a couple weeks ago, little by little.
A couple days before, I had been outside tending to them. Debo was out there w/ his ball trying to get me to play of course. One of the chickens managed to get out of the run & ran around the yard a little. Debo was RIGHT there - it would have taken him a second to get on that chicken if he wanted. But he just looked at it & then turned & looked at me right away!!! I was so glad! I said GOOD BOY! & grabbed his ball & threw it to him. Told him to sit & stay, then I went & rounded up the chicken. Whew! It was tense for a second, but I was so happy w/ the result.
So, a couple days later, I let the chickens out. I did it around 5 in the afternoon, so I would only have to watch them for about an hour or so before they went in the coop for the night. I had worked Debo out previously (so he was tired) & I just had him on the leash, chilling by me while I sat in a chair. We just sat there & watched the chickens. He did good!
In the days after, the weather had been pretty nice, so I made a point to be out in the yard a lot w/ the chickens out & Debo w/ me, to continue getting him comfortable w/ them. I see little signs of less than complete comfort, but I think he's doing well. I make sure to reassure him often when he is being chill. I don't allow him access to the yard when they're roaming unless I'm watching. I accept that there is some inherent risk, but I'm happy w/ the results so far.