RE: Fox coming in for chickens.
As the chickens are fairly easy prey for him i would think he will come back. My advice is get the 12 bore and .270 out and sit in an upstairs window overlooking the chicken pen (if there is one) and try sqeaking him in at around first light. If he gets close before you see him you can use the 12 bore and then if he decides to stop out of range you can drop him with the .270. I dont know much about coyotes as we dont have them here in Britain but the above should work for foxes. Good luck!
Mike