My understanding is that there are more than 2,000 professors at UIUC. I am pretty sure that you cannot take 2,000 very smart people, tell them they are in charge, put them in front of less experienced people, and not have at least a few of them eventually develop significant “unfortunate” personality problems. There will be a few bad professors, or professors with bad personalities (not always the same thing) at pretty much any university (and I have run into a couple somewhere along the way). UIUC is still a very good university.
Physics and math are a very good combination. Physicists will have tough math problems to solve from time to time. The nature of these problems might depend upon what sort of physics they are doing.
Economics and math are also a good combination.
And the right combination of classes / majors / minors for you is something that you can figure out after you get to university and have taken a few courses.
Some form of graduate school is entirely possible with any of these majors. Therefore…
Sticking to budget and avoiding debt would be a very good idea.
I would run the NPC (or have parents run it) and make sure that you are okay with the results before applying ED.
How does this combine with applying ED to Brown? If you get into Brown (a reach for everyone, even more of a reach with a 3.8 GPA) then are you okay with your application to Pomona being withdrawn?
You do not need to apply ED at all. If you do not apply ED anywhere, they you will be able to compare offers before you need to decide where to go.
If you do end up wanting to study in any graduate program, it is very normal to change universities between undergrad and graduate programs. For students who did very well as undergraduate students it is very normal to attend a “pretty good, and affordable” undergraduate school and then go on to a graduate program that is very highly ranked for the specific major. You specifically do not need start at a highly ranked undergraduate university to go on to a highly ranked graduate program.
However, if you want to end up in any graduate program, you need to be able to afford to do it.