Actually, if he assaulted Dylan and Zac (proof exists and the principal seems to indicate it is not the first time). Then he can be charged with that crime (Assault and Battery). Some localities Assault is a verbal threat while Battery is the actual physical attack. In other localities either action constitutes the entirety of the crime Assault and Battery. This is not petty. It can easily be moved to a felony level and often is when underage victims are involved. Further charges of child abuse etc, would just compound the issue. If he is 18 (Possibly even 16 or 17 depending on the DA) he gets charged as an adult. Especially, in the environment post several high profile school events that have occurred (RL). Does not matter about Uncle Dick. The Police and Child Protective Services could make poor Dick's head spin. Aiden would get a new temp address. Liam (future corporate CEO and Karl (Mr Money Bags himself) would have significant influence in the ears of the higher ups in those agencies. Don't waste time with the Beat cops Go straight to the Chief (Needs donations to be reelected) and the local Bureaucrat head honcho. If that were the route taken he would be sweet cheeks (cough, cough) for a bit.
While I completely agree he is petty, a bully. L&P chose to make this some Gordian knot that Sophia cannot unravel. That is his plot device. Does not necessarily reflect the reality that can be imposed.