Check out my activities all updated on MDApps. Suggestions/Comments/Hate mail? I'm lame I know.
My suggestions:
Put your leadership positions from the physics society under one thing on your 15 ECs list. In other words, you can say you were in that society for 2 years as an officer and then talk about the specific positions in the descriptions section rather then putting them in as 2 different things. Same with the Fraternity stuff.
The random student organizations you've listed at the bottom can be mentioned in your CV when you ask for LORs but I'd either put it as extracurriculars not listed elsewhere and just mention in one thing that you held memberships in the following organizations and then give a brief line or two about what their purpose or your purpose for being in them was.
The Head Lifeguard can be considered as leadership in a different sort of way because not all leadership comes from being club officer. Its also in the little things you head up such as being in charge in a job like that. I guess that was a paid job so that can go under the paid employment category to but could also be classified in leadership not listed elsewhere.
Thesis doesn't need to be mentioned separately if it is on the same research you listed above that. The poster presentation should be listed separately however. They even have a separate tab just for poster presentations which differs from the tab for research/lab work tab in type of EC on AMCAS. However in the description for the research you can mention that you are doing your thesis on this research.
As per community service: Are all those miscellaneous activities through a larger organization?? I.e. did you do them with one of your clubs. If not you could list it all under other and then give a description of the kinds of activities you did.
That's 6 slots right there.
For slots 7 and 8 you can individually mention the tutoring program and the overseas program you participated in.
For 9 and 10 you can mention significant scholarships if they are selective scholarships and not just the state scholarship that is given to anyone with a certain GPA and SAT/ACT score cutoff.
For 11, you can mention Deans list and then use the description to say how long you were on Dean's list.
For 12 and 13 you mention your two types of clinical experience: Shadowing and volunteering.
And then if you still have some stuff that you plan on doing and you know you'll be doing it in the near future you can mention it and what you'll be doing.
Do you have any publications pending? Have you attended any conferences? If you think you are weak in an area you can spend this summer to do some extra stuff like volunteering and/or more clinical work, etc.
However I think you have a strong profile.
