I wouldn't let them get too big period. It effects their over all health and can cause spinal damage. Keep them on a mini pig food if you can. House hold scraps like bits of veggies, last night's pasta, etc are great as long as they don't have pork products in them.
I would get them used to being touched. Easiest to do when they are eating in my experience. There is a do/don't debate over it but I hand fed the piglets we had to MAKE them interact with me. But with a PB vs a big farm pig there is less chance of completely losing your hand if somebody decides you were supposed to have a treat in it. Getting bitten can happen. However we hand feed all our keepers on the farm and have yet to be bitten by a food seeking pig. They are taught very early on that being out of the way and then taking food gently when it is hand offered is the way to go if they want to eat. If you shove your hand in a jelly doughnut then try and pet the pig you will be tasted. Clean hands are of little worry.
Good fences. Make sure your fences are tight at the top for predators and the bottom for the pigs. They can pick up most fencing with their nose and just move it out of the way. Have a large dog crate that they are taught to go in to get a treat. That way if they get out you can pull out the crate and more easily catch them, sometimes.
Pigs scream when they are caught or their feet are off the ground. It is a horrible sound and is a defense mechanism. It does NOT mean that they are in pain, but that they dislike the situation and if you were a predator that noise might be enough to startle you to let go. Give them time to calm down and quit freaking out and they'll calm down faster next time.
Watch for the following. Lethargy, not eating, hunched position, looking off, secluding themselves, loose poops, and drinking crazy amounts of water. These are all signs that something is wrong and you should call your vet to get suggestions.
Though the piggies will always be hungry they don't need as much as you might think. They are started off with 1/4 cup of mini pig food twice a day per piggie. Definitely handle them a lot if you want them to be tame. If you plan on harnessing them, it 's best to start young. They don't like things being put over their head. We have only had our PBP for 1 year though and still have a lot to learn. Carrots are an awesome treat.