Initially when they interacted, I stood behind the larger dog, she had a harness with. a handle and sort of straddled her gently and gently intervened if she got too rough with encouraging her to “be gentle” . Over the years she has learned to handicap her play and to just leave the older dogs alone. Having a knowledge of canine body language is essential so you can pick up on your older dog Tommy’s early stress signals so you can give him the space he needs. Hope they answer the questions soon for you. I used to foster care and I do look after dogs and I teach a dog beginner class but I am not a behavioral trainer. I am here to learn what I can too. Hope this helps somewhat