Greetings and welcome to BYH. There's a good bit of shared knowledge and experience in the various threads. Browse around and make yourself at home. Pigs are very smart and very strong, and if they want through that barbed wire, well, they'll just push right on through. A really stout (meaning high output) electric wire (or 2) will tend to keep them from challenging the fence, once they've experienced the hot wire. One acre seems like more than enough space, but depending on what's there, it may not be enough to provide all the nourishment they need. You may still need to provide them food. The coyotes or dogs would have to be pretty serious to try and take on adult pigs. Foxes wouldn't be considered a threat to anything other than young piglets really. We have a good group of active pig owners here, so post away and someone should be along to help you out. Glad you joined up. Hope you stay and share some pics and stories of how it goes for you.
@misfitmorgan @farmerjan @NH homesteader @Mini Horses and there are a lot more hog folks here as well.
Edit to add; you should put at least your general location in your profile so folks can have some idea where you're located. It matters when you ask for help/guidance. Also, there's a member from N Alabama who is presently selling some hogs and they'd be a really good deal for you if you're within reach.