Sorry to hear about the fracture. Where may we ask? How serious is it?
At the risk of sounding like an asshol#, what you describe must happen in almost every game, especially at the older boys ages. The fracture is horrible and your son was unlucky to have sustained such an injury.
Our older son played all the way through until he transitioned to college and our younger son, 02, is still playing. There isn't a game week in and week out that one of the players on the field gets injured enough that he cannot continue. Fortunately, most do not result in fracture or tear of ligaments or muscles.
The perspective might be worth considering in this situation. It is a physical and often violent sport from contact stand point. Coaches and parents are yelling "pressure, pressure, pressure" and some kids are technical enough that he can do so well within the sporting guideline. Many, however, are not and the only thing they know to be responsive to his coach or parents is to do anything to block, stop, disrupt the attacking player.
Refs have a role in this too but they are in loose-loose situation. One one hand, they don't want to let the game get out of hand and have those kinds of injuries, but on the other, these kids are not U8 rec and at this age, they should be able to play the physical game. If your son didn't fracture anything, we wouldn't be having this thread. Its just chalked up as another ugly, physical game.
I do recommend reporting to CalSouth and CSL as its a data point for future rules change and behavior control. No I do not think getting a lawyer or pressing criminal charges is appropriate. Its a part of the liability one accepts when playing soccer. It really doesn't sound like there was malicious intent to harm. It just happened. Just like all other broken wrists, torn ACL, broken collar bone and so on that happens on the field.
Sorry for your son's injury and hope speedy full recovery.