Have you tried Anki? I've seen similar to you situation and student made progress after switching to good Anki decks. If you don't score higher than that - it means you simply are not memorizing details. Unfortunately it's all about memorizing details in step1. It's mostly a memory exam. Seems like you already got some baseline down, now it's time to start memorizing small details and best way to do it imho is Anki. It's easy for me to say, but what timeline are we looking at? Unfortunately Anki might take some time.