You for sure can't ignore the big 3, but let me put it to you this way. Much of the molecular bio that I had was incorporated into a physio or biochem or pharm type question. I left this exam thinking "what aspect of this test was medicine?"
For some reason molecular is big on some of the exams. In hindsight I should have just got up and left, but I kept hoping it would get better. Some of the questions were really bizarre type of research experiments too. For example: removing an organ then putting it back and asking you physiologically what was going on after you put it back. Like how the crap are we supposed to know??? My entire test was like this and it was a joy to get one or two straighforward micro or path questions.
Before I got my scores back, I dug up my old molecular bio book from undergrad with the intention of using it to study in case I failed.
Just pray you don't get the hard molecular version or you are screwed unless you have a solid background in this area. Because think about it: how many practice questions did you come across in Qbank or anywhere else that dealt with a combination of molecular bio and physio for example. If I had studied more molecular on my own I am certain my score would have at least been around 220.
Good luck!