Northwestern is better than Brown for Engineering. I’d choose it over Brown, certainly.
It’s a very, very powerful “brand name”. It’s as if you were worrying that people know Coke better than Pepsi, so to speak. 
Don’t worry. Really.
Do not let your son know about your doubts, as it’d sow doubts not just into his choice, but in his abilities (ability to choose right for his first adult decision, ability to succeed).He’s done amazingly well and got into terrific schools. He’s shown intelligence and character. No reason to doubt his choice. (I know you’re trying to be a responsible parent there, but there’s nothing to worry about. Northwestern is a powerhouse and a huge brand-name.)
Since the COA is a concern and Northwestern didn’t package loans, have him borrow the subsidized portion of the federal (stafford) loans - $3,500. He can “bank” them. If he doesn’t need them, he’ll still have them "just in case. It’ll ease your concerns and will allow him to not work during his first year, or to work very little. However, I wouldn’t turn down the work study. Work study is “pay as you go”, so if he can only work 5-6 hours a week (very, very doable, especially if he can get a job like at the library counter, checking books out) he’ll be paid for that, and if he finds it’s too much and gives his two weeks’ notice, he’ll still have the money he earned at first and he’ll have a few items for his CV.
He may be able to work a little over the summer, to have a litle nest’s egg “just in case”, if that eases your worry.
Northwestern has a medical facility on campus and I can’t imagine there’d be a problem getting his medical supplies.