Sounds promising on the nesting front. Perhaps they really did manage to get their act together! Gestation is about 4.5 weeks, so …. Although peak hoglet arrival times are June and July, so still early. But if there was a female around early, which it seems there was, then it’s possible that she could produce early. Although slightly concerned about her using the same box she’s been in for a while (re. the external parasite position). But, fingers crossed for some hoglets soon. That would be lovely.
Some foxes kill adult hogs as well. I understand a few become specialists. They wait until the hog has unrolled and then pounce. Which is why I never like to hear about foxes and hogs eating side by side. It may be a small minority, but just not worth the risk to my mind. Never know if/when a fox might get the idea for the first time. That’s apart from the leg injuries they can cause. But, even so, I would worry more about a badger being around.
Is the fox entering by the same accessway the hogs use? Or are you able to block, make smaller where it’s entering? I imagine it will be less likely to visit if it isn’t finding any food available, so it’s good that you’ve secured the supplementary feeding area. It might just give up.
Be aware, that some, although apparently not all hogs aren’t too keen on lights which go on and off.
There is talk about human urine (male, I believe, because of the testosterone) putting off badgers and possibly foxes, but not sure if there is any real evidence, but might be worth a try if the fox becomes a problem. I haven’t ever heard anything about it putting hogs off as well, but suppose it’s possible. (More research required!)