I am in a similar situation, however I already have a masters and just started a PhD. I ended up leaving the program after a semester and I am going to pursue clinical research while preparing for medical school. You are in a good position because if you do leave, you can actually a take full time clinical research job (and you will likely be well-qualified for Clinical Research Assistant positions if you were accepted into a PhD program). Many clinical research positions will allow you time to work with patients directly while also conducting research (which you already know how to do), and it would be a great way to explain the transition from a PhD to MD. Jumping ship from a PhD and to work as an EMT or scribe might be a bit tougher to explain, plus you can also work part time as either an EMT or scribe, or even just volunteer if you feel like you are not getting enough patient contact.
I left without the master's because I already have one (and I have a high GPA so it wouldn't help in that regard), but even if I didn't, I probably still would have left. I just did not feel I would get anything more out of the experience in the PhD program. A master's could help you academically, but it could also be a waste of time. If you hate it now, then you will have a long year or two ahead while you finish. You will also need to somehow squeeze in volunteering and preparing for the MCAT, and PhD programs are a pretty big time sink. Also keep in mind that academia is very political and (from my experience) many professors look down on medicine; if anyone in your department catches wind of your interest in medical school, news could spread and it could make things very difficult for you (these people grade your coursework).
Also a major deciding factor should be cost, if you do the master's will you be funded? If not, I would leave, you will already be taking on enough debt with medical school, don't accrue more debt pursuing something you don't want.
And I wouldn't bother worrying about leaving the PhD. People change their minds about things and you can't be sure of something until you try it. Also, it would take you at least 4 more years to finish the PhD and by that point life might get in the way of a career in medicine. But keep in mind that you can't be sure of medicine either, so really get involved in the next few years to be sure this is what you want. Medical schools want you to have lots of patient contact and understanding of what it is like to work in a hospital because they want to be sure you know what you're getting yourself into. I would take time off just to be sure of that because who knows, you might decide to go back to the PhD!
