As everyone else has said, you have done a fantastic job setting yourself up for success and honestly all of this stuff is more than half the battle. As others have said as well, don't get too upset with yourself if you don't honor every clinical rotation. As long as you honor surgery and maybe medicine and peds (+/-), then you keep yourself in that great position.
As far as your question with the chairman, its a great one and one I feel pretty strongly about. I absolutely think you should sit down and meet with him now. When I was a first year medical student I was advised to do the same. I started meeting with the chairman in my first year and then would set up an annual or biannual meeting from there. Dress nice (tie/jacket or whatever is appropriate in Cali, ha), bring in your CV and just ask his opinion of how he thinks you are set up and what you can do to continue to improve your application. The meetings will get less awkward as they go on and you will start to earn some name recognition. That way, when it comes time to do your rotation, he knows you by name and is familiar with you. Furthermore, when it comes time for a letter it will just be easy and he may actually write something personal instead of the standard form, which comes off so much better at interviews. When I had to ask for my letter of rec is wasn't a problem at all, whereas others in my class had to remind our chairman who they were, what they had done, etc.
Those are my thoughts, take them or leave them, but otherwise you're doing great, I'm sure you'll be successful in matching
