I think your plan of attending a career changing post-bacc is a smart one. I can't relate but I think your undergrad GPA is solid and I think it will catch people's eyes when reading your app. If you're really about becoming a physician, take the plunge because you have a good shot if you succeed in your post-bacc.
EDIT: To answer some of your other Qs, it won't look bad if you quit. People change their minds all the time and I think Med Schools will understand. But you better have a reason why medicine was your go-to career change and explain that well in your interview (Tell me about yourself) and your personal statement.
Definitely get more shadowing hours, nonclinical volunteering, and clinical volunteering to make sure you sell them on your commitment to medicine.