Totally agree with Stef. There is no recommended distance, as such, but it’s best not to have feeding and nesting box too close together. As Stef says you wouldn’t want to attract predators to the nest box. But also a nesting Mother may not be too happy having other hogs (especially rowdy male hogs!) congregating right outside where she is raising young ones. But the space you have available might dictate things to some extent.
I would suggest not putting anything resembling bedding in a box you want to use for feeding because it sometimes gives hogs the idea they might want to set up home in there.
Good luck. I hope the hogs approve of your final arrangements for them!