As adults, I feel we need to be careful about the advice we give.
Moving to Boston (or any high cost of living city) and going to school part time without the ability (due to lack of education) to be able to afford to live is not overly realistic. Sure, he could move to a low cost of living area, get a few jobs and build the skills he needs to make a living but probally not in a big city while taking multiple courses.
ROTC could be a path. I do not know but it is extremely competretive but as a second semester sophmore the poster is extremely late to the game. Correct me if I am wrong.
The parent might or might not have paid for next semester but they still could call the school and try to get a refund. The school would likely refuse to deal with the parents but who knows what could happen. If the student is not living in a dorm, it will be very easy to cut off rent and food money.
Joining the military might is an option but even there you need physical fitness. I believe the days of just being a alive to join are long gone. The military can be a great option and career for the right person but it is not a easy path even for those who want to serve. Also I am not sure how they feel about vaping.
Threats are really a losing bet when the other person holds most if not all the cards. As a parent. I would not take kindly to threats. I would view them as a indication of immaturity especailly if that I know are empty unrealistic threats.
In this case, the parent did not appear to be making threats. They make a decesion and carried through. Now the issue is how to change their mind.
What this kid probally need is advice how to deal with his parents. How to diffuse (NOT escalate) the situation. How to negotiate a middle ground. How to pacify the parent long enough to get his education and then leave and never look back if necessary. Some advice was given by not enough. I hope others can give some better advice then I could.