Do-able but it will requires some schedule juggling and careful planning. You will need to check the policies at the college at which you decide to enroll to see if students from one college (College of Business) are allowed to cross-enroll in other colleges (College of Arts and Sciences).
Be aware that non-science majors usually receive a lower priority for enrolling in high demand science classes. This means you may be only find open seats for a class at a undesirable time or with a less popular teacher. Or that you may not be able to take a specific class during a specific semester.
No. So long as you have completed the pre-reqs, have scored high on the MCAT, have strong LORs from your science professors, and have developed the appropriate portfolio of expected pre-med ECs, your chances are as good as anyone’s.
Adcomms really don’t care what your major is.
Most useful business major/concentration for a pre-med-- management. Maybe economics.