I know virtually nothing about the PA program - so I will not even attempt to answer those questions - but I have been involved in several MMIs, on both sides of the equation (as the candidate and as an interviewer/actor).
Nobody knows what made their MMI "stand out" - they may have a "feeling" that something went well, but that's about it. You get absolutely no feedback from the interviewers (or actors), and you never find out what your score is. Also, there are many stations, so you can do amazing on some and awful on others. I would suggest reading up on what the MMI entails, and going through some of the published examples of MMI scenarios. There is usually not a specific response that they are looking for, but there are definitely things they're looking to make sure you DON'T do. For example, if the scenario involves a conflict between yourself and the actor, they don't want to see you get mad and/or blame the actor - that should hopefully be common sense. The MMI primarily judges soft skills and ethics.
The best advice I can give is for you to be calm, well-spoken, empathic, describe your thoughts in a clear, logical and easy to follow manner, and show that you're confident but not arrogant. It is easy to tell you to do those things, but it is much harder to do when you're in such a stressful situation.
That's pretty much all I can say about the MMI - you have to sign confidentiality agreements (even if you're a candidate). In terms of your other questions about the program, since it's relatively small, you probably won't hear from many people on MI who have gone through the program - contacting the admissions people and/or going to a program info session might be more helpful, to get a wider range of opinions. Good luck!
