If you do end up staying in-state, one point in favor of MSU is that (unlike Ole Miss) it’s a member of the National Student Exchange, which would allow you to spend a semester or a full year at another participating school in a different part of the country, for your in-state cost.
For now, shoot your shot at Northwestern ED, and consider having an ED2 plan if NU doesn’t break your way and if you don’t get an EA acceptance you like better than the potential ED2 choices (Rice, Vandy, Emory and WUSTL all have ED2)… and apply EA wherever possible to schools that pass the affordability filter.
(Note that Trinity in San Antonio has Early Action, with decisions by 12/15; if the NPC is favorable there, that could be a nice one to add to your EA list. It’s a school that I think we often forget to recommend, because it defies categories a bit - a LAC that has both business and engineering, meets full need, and is located in a part of the country that has few schools of that type. But it’s an excellent school that seems to check the boxes, if the $ works.)
I guess what you need to figure out is where your “worth paying for” threshold is, when you can go to a well-regarded flagship university for better-than-free. Maybe that’s why the “missing middle” is missing - because you feel like Northwestern and its peer schools are worth going out-of-pocket for, but you don’t have a strong enough preference for schools like Lehigh or Trinity to spend six figures that you don’t have to spend, for an undergrad degree. That’s entirely fair - only you can decide where the cutoff is, in terms of being worth applying.
I would say that Washington & Lee could be worth an application, because they definitely have what you need academically, and on top of meeting full need, they also give their full-ride Johnson Scholarship to 10% of admits. Deadline to be considered for that is December 1st.
As another reach to consider, CMU Tepper is a top-5 business school that’s quite computation-heavy in general, and offers concentrations in Finance and AI, plus a Computational Finance program that takes applications sophomore year. With around a 10% acceptance rate, it’s another long shot, and it has more of a nerd/grind type vibe than most on your list so it might not be a fit in that regard, but it’s something to consider as it would certainly be a pipeline to the kind of work that seems to interest you.