Adopt the Kitty
I think you are worrying a bit too much. We also adopted our boy cat from a shelter, and he was unhappy and afraid to eat. I was a bit stressed too, because we had a dog and I didn't know how they would take to each other. He wasn't yet neutered, and I would never declaw. Well, we got him neutered, he never sprays, and I got him two quite nice scratching posts. I put them near furniture that I didn't want him to scratch and all is fine. If you are nervous, confine the kitty to one room of the apartment, say the bedroom for a trial. Put food, water, litter, scratching post, toys in the room with him. We did this at first until the dog and cat were ready to co-exist. I think you will be quite pleased and so will your precious new companion. Additionally, I have friends who've had great luck with citrus air fresheners as deterrents from bad behavior. Apparently, cats dislike citrus. So you could try that too. But see what happens. All might be fine and you won't need to do that. Good luck to you.