How to make up for only a few AP tests?

So I’m currently a Junior and next year I’ll be applying to some very selective colleges (UChicago, WashU, Northwestern) and due to how my school sets up AP classes I’ve only been able to take 4 AP classes before senior year. I took the AP World test last year and didn’t do too well (3). I realize that’s college credit but not at these places so I won’t send it in. This week I’m taking Bio and Lang and those should be a 5 and 4 respectively but I decided to not take the APUSH test and I now regret that. On a practice test in school I only missed 4 of 55 without studying. What I’m wondering is how will colleges look at me if I only send in 2 AP scores for the 4 taken. Also what can I do to make up for it? I’m already planning on taking SAT subject tests in Math II and BioM, should I add a third one to show knowledge in specific subjects? Add US history? I also need to know soon because SAT subject test sign ups are on the 11th.

If you want to know more about my academic situation I posed more here. http://talk.collegeconfidential.com/what-my-chances/1863760-any-ideas-on-what-i-can-still-do.html#latest

Yeah, I’d do USH and aim for 740+ (though 700-730 is fine). That should broaden your application a bit.