There’s no simple answer to “how much”. You should gain enough shadowing that you feel you have a robust understanding of what a doctor’s job involves. You should shadow as many different specialties as you can, particularly in the primary care fields.
For clinical experience–again no simple answer, but enough that you truly gain a feel for what being around the sick, injured, mentally ill, physically debilitated and their families is like. I would say as long as your clinical position continues to offer insights into how doctors and patients interact and as long as you are learning something, you should continue.
No, but AMCAS asks for the contact information [name, address, phone, email] for each experience , along with start and end dates. (The contact info is in case an adcomm wants to verify your experience.)
It depends on what your eventual career goals are. If you’re interested in applying to research intensive med schools–lots. Specifically, your involvement should be long term and involve significant responsibilities for the success or failure of the project. (e.g. a senior research thesis or similar). If you’re not interested in applying to research intensive med schools and plan to enter into a primary care field, then enough research so that you have a have first hand understanding of the often fraught nature of the research process.
A minority of applicants (~15%) are accepted without any research.
Club memberships are not necessary. You also need to be on the lookout for leadership opportunities since med schools are judging applicants on their leadership potential, among other things.
Impossible to say until you have a MCAT score, but you’re on the right track.