Nutrition and healthy eating is a concern for over 80% of Americans. Most dietitians are still employed in health care facilities like hospitals, clinics and nursing homes where patient care expenses are regulated by third-party reimbursement (Medicare / Medicaid and insurance companies). Perhaps you could get a job in the Air Force as a dietitian or in a veterans hospital/clinic after you leave the military.
I would first determine your interests, career and financial needs, including how long you plan on staying in the Air Force. I would also recommend you talk to an Air Force dietitian employed on your base about what they do and how they like their job as well as opportunities within the Air Force for dietitians. I understand that the military may provide tuition assistance towards college courses for active duty. However, if you continue in active military duty, when you take classes will depend on your military commitment first. Many take night, weekend or online college classes. If you can, sign up for GI bill for education benefits which can be used anytime during active duty or up to 10 years after retiring. You can also transfer the GI bill to your dependent.
Are you interested in food service management or educating people about a healthy diet (clinical)? Depending on whether you are interested in food service management or nutrition, I would take courses in either quantity food production or basic nutrition. Foodservice has a lot of management (people and financial) courses and clinical nutrition has a lot of science (chemistry, physiology, anatomy, and biology as well as psychology).
Have you read my topic Dietitian or Nutritionist? You can read online about how to become a registered dietitian at the Academy of Nutrition and Dietetics as well as educational requirements and accredited college programs. The Academy periodically surveys its members for salary info. The results of these surveys are published in the Journal of the Academy of Nutrition and Dietetics every few years and you can order Compensation and Benefits Survey of the Dietetics Profession. Members provide years of experience, area of practice and income figures to the Academy for these surveys. You could determine if that would meet your needs. The Journal of the Academy of Nutrition and Dietetics is available online, but only available to members or subscribers. You could ask a dietitian on your base for their JAND copy of the last survey.
With your agreement, I would forward your email to an Air Force colonel I know and it would be up to her to correspond with you about her dietetic Air Force experience. Email me back if you want me to contact her on your behalf.