Night time predators need a good fence with an apron. Laying out a length of chicken wire on top of the ground connected to the fence will deter digging predators. I held mine in place with those long fabric garden U shape prongs. Then the vegetation grows up through it. Diggers tend to dig in a tight u shape, close to the fence, the chicken wire prevents them getting close to the fence. On the ground, they can't tear through it.
As a fence, chicken wire is not enough, mine has woven wire fence up about 4 feet on the outside, chicken wire up about 2 feet to keep chicks in. Then I have chicken wire over the top, completely enclosing my run and coop. Raccoons can crawl up a 5 foot fence and down again to eat your chickens. Trust me, I tried this, and lost a lot at night. Once I enclosed the top with chicken wire, I was fine.
You really need to look carefully at the gate, that is generally a weak area of the set up. I buried an old piece of metal directly under the gate, and then placed a piece of a railroad tie that the bottom of the gate is pressed firmly against when closed.
I love to have mine out and about, think they are healthier, a rooster helps, but I also have enough room to keep them locked up. I keep them locked up if I am hit by a predator for a week so the predator moves on, I don't let them out on windy days, I think it interferes with their hearing. Bobbi Jo, recommends not on a real dark cloudy day either, so I do that to.
Yes, you hate it when you lose one, and it is always your favorite, but then you can get more chicks!
Mrs K