Removing a fox will not resolve the problem. Predators are territorial and young foxes that have recently been "kicked out" by their parents are always on the lookout for an available territory and thus hunting ground. The chickens are a non-native, highly-nutritious, and fairly easy (if unprotected) source of food for many of our native predators such as the fox, bobcat, weasels, hawks, owls, etc., as well as species such as raccoon that didn't start out as part of Oregon's predator community but are well-established now. In other words, the chickens are a rich food opportunity that no predator can really afford to ignore.
I strongly recommend building an enclosed run (including the top) to supplement your enclosed night coop, and further, would strongly recommend using hardware cloth or at least 2x4" welded wire if hardware cloth (1/2") isn't available as an option. This is because "chicken wire" is very vulnerable to breaking down over time in the weather, and more importantly, is easily chewed through by most of the mammalian predators that would be lured to the rich opportunity to obtain a chicken. In the best case scenario, you would extend the fencing below the ground surface about 6-12" and then outward in an L-shaped apron out towards predators, some of which can dig quite well in attempts to defeat a vertical barrier.