The current layout looks good, thanks for following up on this so quickly!
A few pieces of info: EE/ToK/CAS aren't really the three most crucial aspects of the diploma, the IB website seems a bit misleading about this. Together ToK and the EE provide three possible "bonus" points out of the the maxumum total of 45. (
http://www.amyscott.com/2010%20onward%20Diploma%20points%20Matrix%20tok.pdf.) CAS is a hurdle requirement which needs to be passed for the diploma to be awarded, but I don't know anyone who has failed. The most important component of the diploma is really the six subjects you must complete, of which a minimum of three must be taken at HL. Each is graded out of 7, so they provide the remaining 42 possible points. With the exception of maths, I don't think it's necessary to separate each subject into HL and SL subforums, because HL is usually just additional content rather than a different syllabus. I do think it would be worth keeping ToK and the EE in separate sections given that they're entirely separate from each other.
(Sorry if any/all of this is obvious, but based on the above posts I wasn't sure that it was understood.)
EDIT: Also, I suggest that you add an IB header to the splash page.