Your GPA is fine, and being captain of the football team and playing sports does look good. However, you're SAT score is a little low (the average SAT score for my entering class was 1090). I would retake the SAT and/or take the ACT. Volunteering looks good on your application and is just a good thing to do in general. Being involved in clubs looks good, particularly if you are a leader within the club. The Citadel admissions process is very holistic; they like to see that you can excel academically and physically, have leadership potential, and have time for extracurricular activities. This shows that you have time management skills, something that is crucial during knob year.
Applications for the next year are generally released around June. I would try to send yours in by July/August. They are pretty quick on making decisions as well. As i recall, i sent my application in at the end of July, and got an admissions decision the first week of September. Once you get accepted, make sure to do a pre-knob visit before making your final decision on whether or not to attend. It's as close a glimpse as you can get of knob year before matriculation day. Keep working hard to maintain/better your GPA and SAT score, and try to do well on your AP tests so that you can get some pre-requisite classes out of the way. Good Luck