Considering it jumped over the fence, maybe run some barbed wire along the top, 4 strands about 6 inches apart. It's a stopgap measure, but if you can't or prefer not to kill it it's your best bet. If you do intend to kill it, then I have a recipe for coyote that would probably work for it. Our coyotes are pretty big and I'm not sure how your fox will dress out, so I'll give you the per 2 lbs of meat measurements and you can multiply it to get the full recipe.
per 2lbs of canine meat (fox, wolf, coyote, dingo, whatever)
1/4 cup of dark soy sauce
1/4 cup of brown sugar
1/4 cup of cane vinegar
2 cups of water
2 bay leaves
1 tsp ginger powder
1 tablespoon of black pepper
1 onion minced
If you've left the skin on and scraped out the hair with a bell scraper, then sear it over a wood or charcoal fire. If it's been totally skinned then skip it.
Cut up the meat into primal joints, put it into a pot with all else and simmer on low for several hours until the meat falls from the bone. You may need to add more water during cooking. But once you fish out the bones and gristle and the bay leaves, tear up the meat and put it back into the gravy and cook it down until it gets a bit sticky like bbq sauce. You can put it with white rice or on toast. It's also good with roasted bell peppers or steamed mustard greens as a side dish.
Regardless of how you deal with your fox problem, I hope you do get it resolved.