What should I do from on out???

Hello, I’m a sophomore, and I’m wondering what the best plan would be for me from here on out regarding extracurriculars. I would love to get into Northwestern (I live in Illinois), and I would like to know if it is too late to start building an application impressive enough to get into a top 20-ish school like Northwestern. So far, I have straight A’s, I’m taking hard classes in a tough school, and other than that, I have done as follows:

Freshman year- member of Key Club/ Model UN/ debate (I know, not too impressive)

Sophomore year- Volunteer Coordinator for Key Club, Treasurer of Model UN, might snag a position in UNICEF; member of debate, science olympiad, math league, and NHS

I’m worried I don’t seem interesting enough, especially as I haven’t accomplished much in these clubs. What should I do instead of getting a lot of volunteer hours and getting a few leadership positions? I was thinking about trying to get an internship at an engineering company (Woodward) or some sort of lab internship this summer, although I don’t know much about engineering and am not sure what I might want to major in (As a side note, how did all of you find out what you wanted to be in high school? Are there any tools on the web I can use to do this?). Do you have any other suggestions for places to get an internship, places that would accept a newbie like me? Also, would trying to get awards/ do well in sci olympiad, math league, and Model UN junior and senior year and possibly starting a sciency-type club look like I’m only doing it for college apps, especially if I don’t create the club by the end of this year? I know I would only be able to get to state max in math league/ sci olympiad, as I’m no science/ math wiz, even though I am very good at it. Finally, would working at Culver’s during the summer increase my chances, and does what I’m doing right now seem too well-rounded, like I’m not AMAZING at anything and don’t have a single passion? (Does not being absolutely great at something matter nearly as much at somewhere like Northwestern when compared with Ivy League schools, as I have clubs that have to do with volunteering, politics, science, and math?) To wrap things up, I’m a white male if that matters, and I DO enjoy the clubs that I’m in and the idea of getting an internship doesn’t sound dreadful to me, aka I’m not JUST doing these things for college apps.

Answers to ANY of these would be much appreciated for such a long slew of questions.

Oh yeah also my state is switching to the SAT next year even though I’m much more familiar with the ACT. Would studying for both be a waste of time (I would much prefer having to focus on one obviously, unless taking only one looks bad), and is going through the whole part of the “red book” that doesn’t include the practice tests a waste of time? What is the best book/ program for tips about the specific ways they trip you up, for both the SAT and ACT? And I might consider a state school like Urbana-Champaign, which would mean I HAVE to take the SAT, correct?

Thanks again