Ok, first off, Good Call on not trusting a dog you dont know. Second.. Do you have a fenced yard? Somewhere you can lure him for the time being?
Yah, be VERY weary of people who respond from craigslist.. I have heard more bad than good from CL.
I agree that the dog needs to be scanned for a chip.
Does he appear well fed? are his nails trimmed or long... Is he neutered?
Continue to be cautious with the dog.. No sudden movements, but dont be rigid either..
I dotn see how cooked chicken, (unless you have seasoned it) could be bad for the dog.. its meat. On the other hand.. You dont know how he is with food either.. he could be a really happy dog who gets protective of food, so there again, be very cautious, (personally, i would go as far as using a stick or somethign to push the food in front of him, not my hands)
I hope you can find a good home for him, or his owners!