Maarten! I was actually worried about you. I cranked out four chapters, and not a word from you! Good to have you back!
Yes yes, I know that you think Will is a horrible person, but he's an important part of the family, and a key protagonist. I think that your annoyance with his childishness has much merit, but he is showing signs of maturing, and he's doing a much better job of controlling his emotions.
JP looks at him and sees that evolution, but he also sees it mixed with a very bright mind, a firm focus on the family, and a decided sense of right and wrong. He's giving Will some crumbs of major responsibility, probably to see how he handles them, and probably to give Will a taste for them.
JP sees Brad's strengths and weaknesses too, and he's probably unwilling to give demerits to Will for dealing with Brad badly, when he himself has a tough time handling Bradley.