Another good primary source for your son, and you, is the DoDMERB home page. Read every menu item on the left; there is a detailed description of the process, FAQs, workflows.
Here, on SAF, an unofficial source, go to the top of the Nominations forum and read the Sticky posts there.
Finally, @MullenLE may well pop up to reply. He is the Deputy Director, DoDMERB, who kindly gives of his time to privately communicate with applicants and future applicants.