@sawdeeka: If I read your post correctly, your 3Q son already has a nom to USNA, so you are done worrying about other applicants in your district. Your son is past that gate. Now his application goes to the academy admissions team to be evaluated against all of those 3Q nominees from across the country vying for the various diversity buckets the academy is trying to fill. Here is an example of class composition for the USNA class of 2022:
Navy doesn’t publish the nominee-to-appointee breakdown the way Army does:
but those on the SA forum boards say they are very similar at a roughly 50% acceptance rate for 3Q nominees.
As for how many spots are open for each of your MOCs for the next incoming class, if appointed, your son will never know to which nominating source his appointment was charged. If the academy wants him badly enough, it can charge him to any open source; it is not not limited to the MOCs from your state/district. Some district’s slots go unfilled due to either no applicants or no qualified applicants and those are free for the academy to charge to. Also, the academy itself has a number of nominations (like the Superintendent’s noms at WP) that it can use for a candidate it wants but who did not win a MOC slate.
Do not waste time trying to figure out percentages and “chances” – that’s futile as you aren’t equipped with perfect (or even reasonable) knowledge of his competition or the available nomination sources. Enjoy this time with your son. If he IS appointed, his life will change drastically in a few months, and you can never get this time back. Good luck to him.