This shouldn't be too bad, if you ask my opinion. I took AP Amer. Gov. this year and while my class was quite difficult (primarily due to a "teacher" who earned such a title only nominally), the actual AP exam was really nothing to be concerned about (I think/hope, as I have yet to see my score
One question: Don't you think it would be better to take a wider range of classes (i.e. not 3 humanities courses) in order to demonstrate well-roundedness for college?
Also--possibly procure an AP Chem review book so you can self-study along with your honors Chem course if you believe that the course with outside study could suffice as preparation for the exam.