Under absolutely NO circumstances should he get
anything from your kitchen

It's illegal for one thing and a disease risk for another.
If stuff is peeled/cooked outside that's another matter and he will benefit from a bit of variety in his diet but I'd avoid bread as it will make him over fat without providing any real nutritional value.
I would disagree with your pig farming friends, he
does need some form of 'hard feed' - pig food is especially formulated to contain all the vitamins & minerals he needs for healthy growth and development. Without it he just won't go and do as well as he should (especially if he's a commercial 'white' pig - they need good levels of feeding) I'd go for 1lb of hard feed for every month of age, up to a maximum of around 5lbs per day. If he's not been in the habit of getting hard feed build him up gradually, two or maybe even 3 feeds per day, plenty of water available for him and don't give in when he squeals for tasty stuff and tries to tell you he doesn't like the pig nuts

I think you'll see quite a difference in him once he's eating as he should - he'll do much better

HTH
Karen