Well, since he works in a security capacity, he's got a security clearance of at least level 3 (which is just under confidential). So when he notifies the military of his intent to marry (which is required) there "may" be a background investigation on you. (more than a 70% probability of this). This means DIA agents are going to be visiting friends and family to "investigate" you to ensure you are not a threat to the country, military, or government. I know it sounds kinda like "big deal" stuff, but it's not. Anytime a military member marries while on active duty, if that military member works in security or has a security clearance of any kind, when they get married the perspective spouse has their background checked more so for the military member they are marrying, than for anything else.
So mom and dad will find out, hands down. On top of that, if you have anything in your past that could affect your relationship with the BF, better get it out in the open now. Better he hears it from you, than from a DIA agent. (DIA = Defense Intelligence Agency). Trust me, DIA *WILL* find out. When they're done, they will know you better than you know yourself. Background investigations take anywhere from 3 to 6 months. Longer if you've moved a lot before you left home for that final time.
Additionally, when you get married, you will be issued a dependent ID card and enrolled in DEERS (Defense Enrollment Eligibility System) for your medical coverage. Your medical will be covered under Tricare - meaning you get dropped from mom and dad's insurance coverage automatically.
So, if I file MFS, keep my name the same
That raises flags with DIA, Tricare and DEERS. You will both be investigated for suspicion of a fraudulent marriage. I've seen it in my day where a couple got married "for the extra money" (the BAH and BAQ) when in a high cost of living area, and then divorcing once they leave that area. The military does not take kindly to that, and the military member could find themselves doing time at Leavenworth. The point with this paragraph is, mom and dad are going to find out, and if they don't hear it from you, I'm fairly certain they won't be showing up for your graduation since they may stop funding it. (The military has tons of education benefits for military spouses and their dependents. My favorite is the Hap Arnold Grant.)
Best o luck to you and yours. Also, any military related questions should be directed to the BF. Some things have changed since my days serving, and he has access to free legal advice at the base legal office. All he may need to do is make an appointment (and you can attend also) and it won't cost a dime.