I would suggest staying on the waitlist and maybe even write a few emails to Dr. Callahan expressing your desire to attend Jefferson. Jeff has a large class, and I assume a pretty significant waitlist movement once May 15th rolls around. But yeah, just be persistent and reiterate with sincerity how much you liked the school and how much you would like to attend it. Good luck!
I've never heard of an "alternate list" at Jefferson. Just the regular waitlist and the "high priority" waitlist. Obviously, being on the high priority waitlist gives one a better shot, but still no guarantees. There were people on the high priority waitlist who didn't get in last year.
In terms of what to do to improve your chances, I agree with the above poster. Jefferson likes to hear that you have a strong interest in attending. Frequent emails to Dr. Callahan are the order of the day. To the extent that you can provide any updates (grades, ECs, publications, etc,), send them in.
I heard of one person last year who emailed Callahan and asked if he could speak with her about his application. She agreed to do so, but the conversation never took place for reasons I can't recall. You may want to consider that. Can't beat having an opportunity to make your sales pitch directly to the Dean of Admissions.
Edit: The request was to speak with Callahan on the phone, not in person. Not a second interview.