I am also applying for c/o '13 at the Citadel but I don't know much about full rides as I'm applying for MC option NROTC scholarship. One of the great financial advantages of the Citadel to me is that they offer additional scholarships to ROTC scholarship winners so that eleminates any issues of uncovered expences. You may look at scholarships on the Citadel page for more information, there is a book you can view (maybe the course selection book?) that is VERY comprehinsive on the scholarships. I do not know of any person who has applied to the Citadel who has not been academically accepted. With that said they were all good candidates who had stats above the average incoming knob. Do remember that he must be accepted physically as well though if he is applying to USMMA it is fair to assume he will be.
I have been to the Citadel 4 times and stayed on the campus their using the athletic, academic, mess and dorm facitilites three of those. Please let me know if there are any campus/ground or misc. questions I can answer for you and feel free to pm me.