You may want to start a new thread in order to get more responses to your question...
But IMO, you do not need to worry so much. If your dog lived in a foster home with cats, then I think all should be well. I would recommend using a baby gate to block off an area of your house so that the cats have a safe space away from the dog - let them get used to each other from a distance and at their own pace. Also make sure you keep your pup as well exercised as possible (based on any limitations that may still be present from the leg injury). A tired dog is less likely to focus excessive energy on the cats. Make sure he has interesting toys to play with as well. If he begins playing too rough with the cats, I would clap your hands loudly to interrupt him, tell him "NO!" firmly, and redirect him to play with one of his toys. Praise him when he listens and leaves the cats alone. He'll need you to teach him that playing rough with the cats is not acceptable. I do not think he will eat your cats, but you'll want to avoid any accidental injuries from him playing too rough. You may also want to start working on the "Leave It!" command on walks so he'll learn to leave yucky dead things alone!
A first pup can be a pretty overwhelming experience, but I assure you it does get easier! There are a lot of experienced members on this board and I would encourage you to keep asking questions of any problems you encounter with your new puppy - people will always be happy to help! I would also recommend attending obedience classess to strengthen your bond with your new pup and to learn to work through issues like the ones you've mentioned. Although breeds do have some common traits and tendencies, breed isn't everything, and the behaviour of your dog is more a result of how you teach it than the instincts that it was born with.
Congrats on rescuing your pup, and I'm sure members would love to see some pictures of your fur gang!
Chase (Friendly Resident Wigglebum) - Border Collie/Lab/Shepherd X
Kailey (Misunderstood Gentle Beauty) - GSD & foster failure #1
Rupert (Gold-Medal Winner of the 3 a.m. Kitty Destruction Olympics
Heidi - RIP my sweet baby girl