The University of Washington is excellent for computer science, as I expect that you know. The U. of Wisconsin is also. Both would also be very good for mathematics, and this is a good combination (and is pretty much what I did, although my degree just says “mathematics”).
Given your interest in economics I might mention that as a math major I took one course in econometrics (quantitative economics) and quite liked it. There is quite a bit of math in quantitative economics – which to me is a big plus since it makes economics more like a science (you can make quantitative predictions and test your theories) rather than a matter of opinion.
I do not know whether U.Washington is a safety for you for CS. I am guessing that it might not be specifically for your major. I am thinking that also applying to Washington State might be a good move.
There are some good universities for CS and math a bit to your north. UBC might be worth considering for example. You might want to also look at Simon Fraser and U.Victoria (the latter might of course be more to your west than to your north).
1520 is quite a good SAT score and should help you. If I had this the first time that I took the SAT, I might take it again more to see whether I could get 800 in math rather than to actually help with university admissions.
Edit to add: I think the fact that you already had a CS internship is quite good, and a bit unusual for a high school student. In terms of ECs I think that you are doing well, and you should do what is right for you.