Oh no, how awful I'm so sorry about Sally. I hope Dillan will be OK.
How about a sonic fox deterrent, like this one from Amazon? The reviews on Amazon aren't very good, but I found some good reviews on chicken forums.
I read something about sprinkling used coffee grounds around the garden, as foxes are meant to hate the smell or something, but I don't know if that's true!
Sounds like once you fix the tops of the runs tonight, they'll be quite secure. I really hope the other buns will be OK xx
So sorry.
Perhaps Dillan can stay can stay inside for a while? Or would it be possible to bond him with the other two?