This is really interesting, thanks for including us.
My advice, after being an old fart in grad school, is to pick a topic you’re interested in, that is manageable, and that is narrowly focussed. I think you have that in mind with your three New England/Boston ideas. Your Midwest sounds more broad, which can lead to more extensive research and difficulty crystallizing your final product.
I also think you’re showing that you’re smarter than the youngsters by picking something outside the norm, and perhaps somewhat outside of your experience. School is a learning experience, after all: you get an "A" for concept in my book.
Seafood, of course, is great, but the budget issue is dicey. Jim makes a good point that you could do some fish dishes with the homestyle/budget or Italian takes. If you decide to go old-fashioned homey you might discover that there are more similarities with Southern food than many people think (like the use of salt pork and bacon). Might be a winning concept with your audience.
Lots of luck!