Sorry to

but on questions 3 and 4 (leadership and research) are we expected to include activities and descriptions even if already included on AMCAS? It just seems redundant to me but I may be missing something here.
I used activities that I included on AMCAS... especially since it asked for activities that mean the most to you.
But I wrote information that I didn't get a chance to address on my AMCAS. For the leadership activity, I talked about my leadership position in an evolutionary biology research lab. In my AMCAS, I mostly described what the research was and briefly my role in each position I had held, emphasizing the research aspect. For the Rush Supp, I didn't mention what the research was about (since it's only asking for leadership), and really went more in depth in exactly what I did as a leader, and expanded on what I had gained from that experience. So it sounds nothing like my AMCAS app.
Then for the research question, I wrote about the neurobiology lab I work in now. I talked more in detail about a different research project that I didn't really get to mention in my AMCAS app. Especially because I'm second author on a paper in submission (which didn't happen until after I submitted AMCAS), so I got the chance to add that in there. And of course, I mentioned what I have gained from that experience. I've worked on multiple projects in this lab, and I was sad I really only had room to talk about one project on AMCAS, so I picked another one for the Rush Supp.
So basically, I chose the same activities, but put different spins on them by either describing a different aspect or by emphasizing different qualities. I agree with
chrisoc13 that sometimes it really seems like these schools don't look at your AMCAS app (which is depressing, considering how much time I spent on it) especially after realizing that most supp applications ask the same exact questions as AMCAS. But you still never know, so I always try to put a different light on my experiences, or at least try and re-write it so it doesn't sound the same as AMCAS.
Hope this helps!